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diff --git a/pcl/Anomalies.txt b/pcl/Anomalies.txt new file mode 100644 index 000000000..3a7406ffe --- /dev/null +++ b/pcl/Anomalies.txt @@ -0,0 +1,937 @@ +Overview: + +Though designed to emulate the HP Color LaserJet 5/5M, there are several areas +where the behavior of the Artifex interpreter differs from that device. The +first part of this document provides an overview of these differences, and +the second part notes specific examples in the PCL 5c FTS where the differences +between the Artifex interpreter and the HP implementation are apparent. + +Overview: + + Fonts + Since the release of the LaserJet III in 1989, successive printer products + from HP have shifted away from using bitmap fonts toward scalable fonts, + originally using Intellifont fonts and more recently TrueType fonts (using + the InfiniFont packaging technique). The Color LaserJet 5/5M represents an + intermediate stage in this development. It has a single bitmap font (line- + printer), a primary set of scalable fonts in Intellifont format, and an + additional set of fonts in TrueType format. + + Artifex is not a font vendor, and the default set of fonts offered with the + interpreter is not meant to exactly emulate the offerings of an HP product. + In addition, the default font set corresponds to a later stage in the + evolution of HP products; more similar to the monochrome LaserJet 5/5M and + the LaserJet 6P than the Color LaserJet 5/5M (which more closely resembles + the font offering of the monochrome LaserJet 4 series). Though the set of + typeface "names" that are supported is similar, the format in which these + fonts are stored and some aspects of the supported character set vary. + + This discrepancy in font offerings has many visible manifestations, most of + them quite minor. Some of the more obvious differences are: + + 1. Spacing. + + Not all of the proportionally spaced fonts in the default set match + the spacing (advance width) of the corresponding fonts provided + by HP. This is most often visible when lines of text are set up to be + clipped at the right margin (rare in applications but more common in + the FTS), or when the automatic line wrap feature is used. + + 2. Adherence to requested height and/or (fixed-width) space. + + In normal operation, a PCL document does not directly specify which + fonts are to be used for a given block of text. Rather, the document + will specify a set of font properties which the interpreter attempts + to match as best possible given the set of available fonts (the rules + which define a "best" match are quite specific). Among the properties + specified are the height of the font and, in the case of a fixed-pitch + font, the character pitch. + + All of the fonts provided in the default set for the Artifex + interpreter are scalable, hence all will exactly adhere to the + requested font size and/or pitch. In situations where a bitmap font + would, instead, be used by an HP printer, only an approximate match + may be available for font size/pitch. Hence, the size of text + rendered by the Artifex interpreter may differ from that of an HP + printer. + + 3. Interaction with downloaded symbol sets. + + All of the fonts in the Artifex default set are TrueType fonts, which + make use of the Unicode font encoding scheme. Intellifont fonts, such + as the base set provided with the Color LaserJet 5/5M, make use of a + different font encoding scheme known as MSL. (In principle there is no + connection between a font's scaling technology and its encoding scheme, + but in practice all Intellifont fonts use the MSL scheme and all + (unbound) TrueType fonts use the Unicode scheme.) + + In PCL, a user defined (downloaded) symbol set may apply to either the + Unicode or the MSL encoding scheme, but not to both. Hence, a downloaded + symbol set that uses the MSL encoding can be used with the base font + set of the Color LaserJet 5/5M, but not with fonts provided with the + Artifex interpreter. Conversely, any downloaded symbol set that uses + the Unicode encoding can be used with the base font set of the Artifex + interpreter, but not the Color LaserJet 5/5M. + + Because support for the currently selected symbol set is the highest + priority selection parameter in the PCL font selection mechanism, this + difference in font format can have dramatic effects, as is evident in + some of the 5c FTS tests. + + 4. Font scaler anomalies + + The set of Intellifont fonts distributed by Agfa includes fonts with + some "malformed" character outlines (outlines that do not adhere to the + documented format). These outlines are handled differently by the + HP Intellifont scaler and the scaler provided with the Artifex + interpreter. For example, in the 5c FTS, the lower case 't' in the + Park Avenue font has a malformed outline, and its rendering with the + Artifex interpreter is quite different (i.e., distorted) from that + produced by an HP interpreter. + + Rendering Methods/Halftones + + HP's documentation identifies 20 different "rendering algorithms" that can + be selected on an object-by-object basis. For the most part these rendering + algorithms represent different halftones, though certain rendering + algorithms also specify color mapping (in particular, color to monochrome + conversion). + + No actual devices support all 20 algorithms. For any given device, many + algorithms are mapped to others, so that no more than 6 to 12 unique + algorithms are supported. This remapping respects color transformations: + a monochrome algorithm may be remapped to another monochrome algorithm but + not to a color algorithm, and vice-versa. Hence, the remapping of render + algorithms is essentially a mechanism for selecting amongst different + halftones. + + Halftones for PCL 5c devices fall into two categories: "predictable" and not + "predictable". Prior to the release of the Color LaserJet 5/5M, all PCL 5c + halftones were predictable: all halftones were based on threshold arrays + (HP's documentation terms such halftones "ordered dithers", because they + have a monotonicity or "order" property), and the same halftone was used on + all devices. (Strictly speaking, there is "upward compatibility": some + devices offer more halftones than others, but when a halftone is offered on + multiple devices it is the same.) + + The Color LaserJet 5/5M completely broke with this tradition, and offered + only "unpredictable", or device specific, halftones. This was accomplished + by adding five new halftone algorithms to the previously existing set of 15, + and on the Color LaserJet 5/5M, remapping all of the existing algorithms + that require halftoning (algorithms 1 and 2 do not) to these five. + + The "predictability" of a halftone is potentially of great significance in + PCL 5c, because of the manner in which HP chose to implement raster + operations. These are defined on a pixel-by-pixel basis after halftoning + (at least, where such a definition is possible; see the contone discussion + below for further information). Hence, when using raster operations to + combine objects rendered with two different halftones, the order in which + a halftone darkens pixels is of great significance: given two objects of + approximately 50% intensity and an exclusive-or raster operation, the + resulting region may be solidly colored, fully white, or anything in + between. + + The Artifex interpreter provides the full set of rendering algorithms that + use "predictable" halftones, and except for the case of the noise ordered + dither, the halftone used is identical to that used by HP devices prior + to the Color LaserJet 5/5M. The halftone provided for noise-ordered + dither is only roughly similar to that provided by HP, but this should + not cause a problem in practice. Though in principle "predictable", the + noise ordered dither used on HP devices is so large (128 x 128 pixels) + that no application could reasonably take advantage of its ordered + property. + + The Artifex interpreter provides no device-specific halftones because it + is impossible to know a priori what output device it will be used with. + Mechanisms are provided to allow device-specific halftones to be assigned + to specific rendering methods--see the accompanying interface description + for more information. All of the rendering algorithms that would normally + use a device specific halftone have been remapped to a method that uses + a predictable halftone. A mechanism is available for modifying this + mapping; again, see the interface document for details. + + The Artifex interpreter supports user-downloaded threshold (dither) arrays, + which are supported by all recent HP color devices except the Color + LaserJet 5/5M. If desired, this support can be disabled by remapping the + corresponding render algorithms (9 and 10) via the mechanism noted above; + by default, however, these are not remapped. + + In practice, this implies that halftoned output produced by the unmodified + Artifex PCL 5c interpreter will have a very different appearance from that + produced by the Color LaserJet 5/5M, even when the former is output on the + 5/5M. (There are also other complications, which are described further + below.) In general, the output from the Artifex interpreter will be similar + to that of the original Color LaserJet and the HP DeskJet 1200 and 1600 + C/CM printers. This is a reflection of a different configuration rather + than a fundamental difference in the interpreter. + + Raster Operations, device pixel depth + + In any industry that undergoes rapid technological evolution, any technical + term that becomes significant for purposes of marketing tends to lose its + technical meaning, as manufacturers shift the definition to show their + products in the best light. Such has been the case for the term "resolution" + when used with respect to inkjet and laser printers. + + HP does not provided a resolution specification for the Color LaserJet 5/5M. + It does, however, claim "1200 dpi" equivalent performance, via the use of + "resolution enhancement technology" (RET). + + Based on the traditional metric, namely, the thinnest horizontal and + vertical pure color line that can be drawn, the Color LaserJet 5/5M is + a 300 dpi device. The resolution enhancement technology used by HP + provides for more rapid modulation of the laser in the fast-scan + direction (the long edge of a letter or A4 page). This is used as part of + a halftoning technique that produces thinner lines in the slow-scan + direction than would be indicated by the 300 dpi resolution. This makes + the printer somewhat of a contone device, with between 8 and 16 levels + per pixel in each color plane. + + Based on empirical evidence, HP does not make use of this contone capability + in a direct manner. Rather, the level used for a specific pixel is based + both on the color of that pixel and on the colors for a small number of + nearest neighbor pixels. A likely reason for this is that PCL rasters are + traditionally bi-level in each color plane (this is true for all of the + default or "fixed" color palettes), and the printer will only support + input resolutions to 300 dpi. + + A side-effect of this arrangement is to make the effect of general raster + operations completely unpredictable; indeed, much less predictable than + would be indicated by usage of "unpredictable" halftones. For actual + applications this is almost never visible, but in several of the tests + in the PCL 5c FTS, the results on the Color LaserJet 5/5M bear only + slight resemblance to what is documented and what is produced by other + PCL 5c printers. In these cases, the Artifex PCL 5c interpreter + follows the documentation, as the results produced by the CLJ 5/5M seem to + be extremely specific to that device. + + Color Correction + + The Color LaserJet 5/5M provides sets of two device dependent and three + device independent color spaces. One of the latter is not, however, a fully + device independent color space: the "Colorimetric RGB" space is documented + as a device independent color space but is implemented as a set of lookup + tables based on the device-dependent RGB space (all above board: this + arrangement is noted in the documentation). + + The implementation of the device dependent color spaces is simple enough, + with the exception of some peculiar color correction applied to the fixed + color spaces. The latter is discussed below. The implementation in the + Artifex code matches that of the Color LaserJet 5/5M quite closely in this + area, with the exception of the color correction anomaly. + + The device independent color spaces are another matter entirely. Nothing can + be said directly about the "Colorimetric RGB" space since this is not + actually supported. The documentation for this format does, however, include + several parameters whose significance is, at best, obscure. The definition + of the chromaticities of the primaries is straightforward enough, and the + specification of gamma parameters for the components is reasonably + standard (though why the language provides for both a per component gamma + specification and a per-component, per-color-space lookup table is less + clear). The gain parameter, on the other hand, is not standard, and we + could find no description in the literature as to what it might mean. Based + on empirical work using the luminance-chrominance color space (which uses + the same parameter for its base color space), we have implemented the + gamma and gain parameters as: + + out = 1.0 - (1.0 - pow(in, 1/gamma)) / gain + + The CIE L*a*b* color space provided by the Color LaserJet 5/5M is also + somewhat peculiar. Its most unusual property is that an L* value 0 does not + yield black but rather a fairly solid red. This leaves one at somewhat of a + loss as to what the L* parameter is intended to correspond to. In any event, + after prior discussions with the OEM customer, the Artifex interpreter + was built to use the CIE specified conversion from L*a*b* to XYZ (the + color rendering dictionary converts the latter to device colors). The + difference between the two is visible in several of the tests of the PCL + 5c FTS. + + The default color correction information provided with the Artifex + interpreter assumes the output device has uncorrected SMPTE primaries. This + is, of course, not likely to be correct for any actual output device. The + output observed using device independent color spaces will be incorrect + unless a suitable color rendering dictionary has been installed. How this + may be accomplished is described in the accompanying interface document. + + Device dependent color correction + + The fixed or "simple" color space palettes provided with the Color LaserJet + 5/5M are ostensibly variations of the device-dependent RGB color space. + However, unlike the latter, the "simple" color spaces produce different + results when used for raster as opposed to geometric objects: red becomes + orange, green becomes notably lighter in shade, cyan becomes nearly blue, + and blue becomes deep purple. This effect is quite noticeable and is only + present on the Color LaserJet 5/5M; other HP printers do not show this + effect. + + Because rasters rendered with the simple color spaces generate output much + more "quickly" than rasters generated with the equivalent writeable color + palette by a factor of about 3, it is our belief that the simple color + space raster palettes represent the true colors of the device primaries, + and that color correction is applied to colors used with geometric objects + to make them more nearly match what is expected of these colors. + + The Artifex PCL 5c interpreter does and, and indeed cannot, provide the + same form of correction. In the 5c interpreter, geometric and raster + objects that use the same color will have identical appearance. Hence, + rasters produced with simple color space in the Artifex interpreter will not + have the same appearance as those produced by the Color LaserJet 5/5m. + + View Illuminant + + For reasons that are likely specific to the implementation, the view + illuminant setting on the Color LaserJet 5/5m only affects rasters, not + geometric objects. The Artifex interpreter does not replicate this + behavior: the view illuminant setting affects all output. This leads to + different output on one of the tests of the PCL 5c FTS. + + Default Colors + + HP specifies that up to the first eight entries of each palette be given + a set of default, device dependent primary colors. Furthermore, these colors + are not affected by color lookup tables for the device independent color + spaces, but are affected by lookup tables for the appropriate device + dependent color space. + + This effect is difficult to achieve given the design of the Artifex + interpreter and its underlying graphic library. The effect is also of + questionable merit: why use a device-dependent default color with a + device independent color space? Hence, in the Artifex interpreter, the + default colors used with device independent color spaces are themselves + device independent, and are affected by all applicable color lookup + tables. + + Transparency + + The implementation of transparency in the Artifex PCL 5c interpreter + closely follows that of HP interpreters, with one major exception. In HP + interpreters, the determination of which colors are white is made at the + device level, immediately before dithering. In the Artifex interpreter, + the same determination is made at the source color level, after consider- + ation of the black and white reference points but before any other color + transformation. This is arguably a bug but one that is difficult to remedy + given the design of the underlying graphic library. + + In practice, this difference is not visible in application files, and is + visible in test files in only two cases: when using an inverting color + lookup table, and when using rendering algorithm 2 (map black to white and + all other colors to black). Both of these situations arise in a small + number of tests in the PCL 5c FTS. + + Pixel Placement + + Though the definition of pixel placement is consistent across all PCL 5c + implementations from HP, the set of objects affected is not. In all cases + pixel placement affects rectangles in PCL and polygon fills in GL, and do + not affect PCL rasters. For all devices except the Color LaserJet 5/5M, + pixel placement does not affect text; this is also the documented behavior. + For the CLJ 5/5M, pixel placement affects the rendering of scalable fonts, + but does so in a manner not consistent with its effects on other objects + (an extra pixel is added on each side of the character, as opposed to just + the right and bottom sides). + + The Artifex PCL 5c interpreter adheres to the documented behavior: only + PCL rectangles and polygon fills in GL/2 are affected by pixel placement + (currently there is a bug that causes the pixel placement command in + GL/2 to have incorrect behavior, but the design intent is as stated). + + Driver configuration parameters + + The Artifex PCL 5c interpreter does not implement the driver configuration + command. This causes several tests near the end of the PCL 5c FTS to + produce different results than is the case for the Color LaserJet 5/5M. + + + +Difference in specific tests of the PCL 5c FTS + +54: + + The line "12345..." is printed in an 8 pt. version of the default + proportionally spaced font. In the Artifex interpreter, this is a Times + font, as it is for the Color LaserJet 5/5M, but not with the same spacing. + +65, 75, 85, 95, 103: + + The raster in each of these tests is printed in a "simple" color space + (fixed palette). As described above, the colors in these color spaces + vary between geometric objects and rasters for the Color LaserJet 5/5M, + but not for the Artifex interpreter. Hence, the colors for the raster + will appear different in the two interpreters. + +140, 143: + + The vertical bar character is from the bitmap lineprinter font on + the HP and from the Courier font on the Artifex interpreter, hence + the differences in the length of the bars. + +273, 274, 275, 276, 284, 285, 286: + + Symbol set differences. + +310, 320: + + These two panels are printed with the printer's "line printer" font. + On the HP DJ 1600C/CM and the CLJ 5/5M, this is a bitmap font that is + not scalable and is offered in only one size, hence its size does not + change with pitch. On the Artifex system, the scalable Courier font is + substituted for the line printer font. This font does change pitch as + requested in the tests. + +403, 412: + + The Univers Condensed font provided with the Artifex PCL interpreter + has all characters condensed. In the version of the same font provided + by HP, certain "universal" characters (characters that are independent + of font style), are not condensed. + +411 (et. al.): + + The lower case 't' in the downloaded Park Avenue font contains a malformed + outline. This is handled differently by the Intellifont font scaler + provided with the Artifex PCL interpreter than by the scaler provided with + HP PCL implementations. + +422: + + The default vertical offset applied to floating underlines by the Artifex + PCL interpreter is not the same as that provided by HP PCL interpreters. + +441 - 443, 450 - 512: + + The fonts provided with the Artifex PCL 5 interpreter are TrueType fonts, + which use the Unicode encoding scheme. The corresponding fonts in the + Color LaserJet 5/5M are Intellifont fonts, which use the MSL encoding + scheme. Thus, downloaded symbol sets that use the MSL coding scheme + can be used with the resident fonts of the Color LaserJet 5/5M, but not + with the resident fonts provided with the Artifex interpreter. Similarly, + downloaded symbol sets that use the Unicode encoding scheme can be used + with fonts provided with the Artifex interpreter, but not with those + provided with the CLJ 5/5M. + +520, 521: + + Symbol set discrepancies. + +680 - 682: + + These rasters are generated in a simple color space, and thus have the color + anomalies described in the first section of this document. + +701: + The length of the bitarray for the third and fourth pair of raster + (magenta and yellow) differ from those on the HP CLJ 5/5M. + + The output of the Artifex interpreter matches that of the HP DJ 1600C/CM. + The output of the CLJ 5/5M is contrary to the documentation, and likely + a limitation of the particular implementation due to the interaction + between rasters and the hardware dither method. + +714: + + On the Color LaserJet 5/5M, two of the white gaps between the cyan lines + appear to be wider than the others (after the 48th line and 98th cyan + lines). These larger gaps are not present in the input data, and are + probably due to a resonance phenomenon between the raster and the + resolution enhancement technology used by the CLJ 5/5M. This behavior + is not reproduced in the Artifex PCL 5c interpreter. + +721: + + This raster are generated in a simple color space, and thus has the color + anomalies described in the first section of this document. + +722: + + On the Color LaserJet 5/5M, the first of the shorter, magenta raster lines + appears to be thinner than the others. In the input data all of the lines + are the same width, and there is no apparent reason for the thinness of + the first line. The Artifex PCL 5c interpreter does not replicate this + anomaly. + +750: + + In the third row, the row with the greatest reduction in scale, the first + (thinnest) bar of the raster completely disappears on the Color LaserJet + 5/5M, but not with the Artifex PCL 5c interpreter. + + Whether a given artifact of a raster appears or disappears when scaled down + is a property of the specific raster scale implementation used. There is + no reason to expect the results to be the same across two implementations, + and little reason to try to make them the same. + +765: + + The output produced by the Artifex interpreter appears to be correct and + agrees with the output of the DJ 1600C/CM. The output on the CLJ 5/5M + differs, quite probably due to a physical limitation of the printer. + + This example involves scaled PCL rasters. Such rasters are clipped to the + the page's printable region. In PCL, a page is always assumed to have a 1/6" + unprintable margin. For this test all three of the rasters present are + scaled by a factor of 14.5. The middle (green) raster in the example has a + width of 25 samples, and is placed 205 pixels to the left of the right + printable margin. Hence, all of the first 14 samples should be visible + (14 * 14.5 = 203), as well as two pixels of the 15th sample. + + In this test, all raster sample lines are the same, and consist of the + following pattern (0 == white, 1 == color, either dark blue or green): + + 0000 0001 0000 0011 0000 0111 0 + + Hence, the 15th sample value is colored, and a two-pixel-wide sliver of this + sample should be visible. + +800 - 804: + + Each of the "bars" in these test are rendered in a different color space, + in the sequence RGB, CMY, Colorimetric RGB, CIE L*a*b*, Luminance- + Chrominance. The final three bars are in device independent color spaces, + hence their appearance will vary based on the color rendering + dictionary provided. + + Note also that fourth bar in tests 800 and 803 reflect the implementation + of the CIE L*a*b* color space in the Color LaserJet 5/5M, which renders + colors with the value of L* = 0 as red rather than black. + +811 + + Each raster in this example is rendered in a different color space, in the + sequence RGB, CMY, Colorimetric RGB, CIE L*a*b*, and Luminance-Chrominance. + Hence, the appearance of the last three rows will depend on the color + rendering dictionary provided. For the fourth raster, the different + implementations of the CIE L*a*b* color spaces is also evident. + +813: + The first two rasters are printed in RGB and CMY color spaces, with the + white and black points reversed. Due to an error in the implementation + of transparency in the CLJ 5/5M, this causes BOTH white and black to be + considered transparent, which in turn causes the center region to be + fully transparent. + + The Artifex implementation does not have this bug, hence either the + black triangles or the black background of this region is visible. + + The additional three rasters are printed in device-independent color spaces, + hence their appearance is dependent on the color rendering dictionary + provided. + +830, 831: + + A number of differences between the Artifex PCL 5c interpreter and the + CLJ 5/5M are visible in these tests: + + 1. The Artifex PCL 5c interpreter, in its default form, supports the + rendering methods with predictable halftones, and does not support + the rendering methods with unpredictable or device-specific halftones. + The CLJ 5/5M has the reverse arrangement. In particular, the Artifex + interpreter supports user downloaded dithers, which the CLJ 5/5M + does not. + + 2. The Artifex PCL 5c interpreter determines which pixels are "white" + for purposes of transparency prior to the effects of the color mapping + implied by the rendering algorithm; the CLJ 5/5M makes this same + determination after such color mapping. This is most visible in the + case of render algorithm 2 (prominent horizontal black lines in both + tests), where the output from the Artifex interpreter is transparent + while that of the CLJ 5/5M is opaque. + + 3. The Artifex PCL 5c interpreter, in common with most HP implementations + of PCL 5c, implements render algorithm 1 (snap to primaries) after + applying gamma correction. The CLJ 5/5M is exceptional in this area in + snapping the colors to primaries before applying gamma correction. + Hence, when using render algorithm 1, the output of the Artifex + interpreter (and most HP PCL 5c interpreters) is always a solid + primary color, while for the CLJ 5/5M it may be a halftoned color. + This difference is visible in the latter part of test 831. + + 4. The final two columns of tests 830 and 831 represent a non-solid + raster object combined with a non-solid foreground, using logical + operation 252. Especially for the larger gamma values, the appearance + of the result is critically dependent on the nature of the halftones + used for the raster and the foreground. In the Artifex PCL 5c + interpreter, the halftones used cause these regions to become white + more rapidly than is the case for the CLJ 5/5M. + +833: + + Each pair of lines in this example constitutes a pair of rasters. The + data for each raster pair is the same, only resolution is changed. + A bug in the CLJ 5/5M interpreter, also evident in test 701, results in + the improper rendering of raster output at 100 and 150 dpi in some + situations. The Artifex PCL 5c interpreter does not mimic this bug, + hence the different appearance of the output. + +853: + + The modified render algorithm referred to in the fourth line of this test + is render algorithm 10, monochrome user defined dither. This render method + is supported by the Artifex PCL 5c interpreter (in its default form), + but not by the CLJ 5/5M. Hence the different appearance. Note also that + the final foreground for the fourth line is used to draw the text for + the final, fifth line of the test, so its appearance is modified as well. + +860 - 865: + + See discussion for test 830 and 831. + +866: + + The different appearance of this test between the Artifex PCL 5c + interpreter and the Color LaserJet 5/5M is due to the different halftones + used. + +871: + + The final three rows of rectangles in this example are rendered in a device + independent color space, hence their appearance will depend on the nature + of the color rendering dictionary provided. In the default configuration, + these rectangles have a yellow hue where white would be expected. + +883: + + The output from the Artifex PCL 5c interpreter matches the documented + behavior, and the behavior of HP implementations other than the CLJ 5/5M. + For reasons that are not clear, the CLJ 5/5M will print a faint outline + of "Text" for the rightmost instance of this string in the first line + of the test. Examination under magnification reveals that this outline + is smaller than the design resolution of the device, so this may be a + print engine artifact. + +956: + + The rectangle on the right is printed with a transparent pattern. This + produces the expected output on the HP 1600C/CM and with the Artifex PCL + interpreter. It does not produce the expected output for the HP CLJ 5/5M, + apparently due to a bug. + + +974: + + See the discussion for test 830. This particular example also demonstrates + a situation in which different color mapping methods are being used for the + foreground and the raster being printed. For reasons that are not yet + clear, this (highly unusual) combination is not properly supported by the + graphic library underlying the Artifex PCL 5c interpreter. + +980, 981: + + 1. The raster operation mechanism of the CLJ 5/5M is broken, and thus + cannot be used as a reliable comparison (see notes at the start of + this document). + + 2. The implementation of opaque text for scalable fonts in the + Artifex PCL 5c interpreter is somewhat imperfect. The implementation + requires both inside and "outside" of a path to be filled, in + independent operations. The two filled regions do not join exactly, + hence a faint outline of the original character is usually visible. + + 3. When compared to the documented behavior, the behavior of the Artifex + interpreter varies in some of the opaque source, transparent pattern + cases. We have not yet analyzed why this is the case, but do not + expect it to cause difficulty in practice. + +983: + + The behavior of the Artifex PCL 5c interpreter matches the documented + behavior, and the behavior of HP devices other than the CLJ 5/5M. Raster + operations on the CLJ 5/5M are broken. + +1053: + + The behavior of the Artifex PCL 5c interpreter matches the documented + behavior, and the behavior of HP devices other than the CLJ 5/5M. The + behavior of the CLJ 5/5M is apparently a bug. + +1074 and 1084: + + The artifex interpreter's implementation of fill type 3 and 4 + (FT) differs slightly from HP. Artifex gl/2 vector fills always + radiate away from the origin in plotter units space. This can + cause slight discrepancies as evidenced in these two frames. + +1070: + The artifex interpreter always fills along +x and +y for hpgl/2 + vector fills. HP apparently fills in a direction related to the + direction of the graphical objects. We believe our interpretation + is follows the HP spec. + +1272: + + The gl/2 interpreter places scalable characters slightly to the + left, the discrepancy for a font scaled to 2" is about 1/16". + Attachment 1 below illustrates the problem. The GL/2 Label is + drawn then we return to pcl maintaining the current "y" coordinate, + select the same font and print the same string. The Artifex + interpreter produces the same output for each string, the expected + result. HP does not. + +begin 664 gl2chbug.pcl +M&T4;)3!"24X[4%<P.T94-"PV,RXU+#`[4$$P+#`[4E(U,#`P,"PU,#`P,#M0 +M5S`N,C4[1E0T+#4P."PP.U!!,"PP.U)2-3`P,#`L-3`P,#`[4%<P+C4[1E0T +M+#$P,38L,#M003`L,#M24C4P,#`P+#4P,#`P.QLE,4))3CM34#$[25`[4%<P +M+C`T.U-$-"PQ-#0L,BPQ+#<L-#$P,3M003`L-3`P,#M,0E!#3`-003`L,#L; +5)3%!&RAS,30T5ALH<S%04$-,&T4* +` +end + +1402 (et. al.): + + The filling of GL/2 polygon regions with lines in the Artifex PCL 5c + interpreter is not completely accurate. Line space and phasing are both + incorrect. These bugs are present in many other GL/2 tests as well. + +1422, 1423, 1424, 1445, 1446, 1462, 1463, 1801, 1803, 1811, 1817, 1894, 1895, 1941, 1946, +1950, 1951, 1960, 1961, 1962, 1963, 1964, 1965, 1966, 2210 (page 1), 2220 (page 2) + + Artifex GL/2 contains minor discrepancies with anchoring line + fills. The problem is more evident in cases where scaling is + specified. Low priority. + +1463, 1463: + + The patterned line fills used in these two tests vary in appearance + between the CLJ 5/5M and the Artifex PCL 5c interpreter because + the latter does not properly set the phase of GL/2 line fills. + +1601, 1602: + + The GL/2 label printing command ("LB") in the Artifex PCL 5c interpreter + does not set the initial position of text correctly when printing in the + vertical direction. + +1641: + + The handling of horizontal tab in GL/2 differs between the Artifex PCL 5c + interpreter and the CLJ 5/5M. + +1642, 1650: + + The position of the label origin in GL/2 varies between the Artifex PCL 5c + interpreter and the CLJ 5/5M. + +1680: + + The character sets supported by the fonts used in Artifex PCL 5c + interpreter, in its default form, are not the same as those supported by + the fonts in the CLJ 5/5M. + +1752, 1753 (et. al.): + + The lower-case 'a' in the GL/2 stick font provided with the Artifex PCL 5c + interpreter is a different style than that of the stick font in the + CLJ 5/5M. This difference is also evident in other tests. + +1860, 1862, 1863: + + The position of the GL/2 label origin in the Artifex PCL 5c interpreter is + not accurate. This is particularly noticeable for arbitrary transformations + of text, as in the first two tests cited. + +2080: + + The scaling of the rightmost imported image in this test is + different than the HP printer. The artifex interpreter complies + with the HP PCLTRM. The following test shows that simply entering + and leaving HPGL/2 <ESC>%OB<ESC>%0A has the side effect of + resetting HPGL/2 scaling. This should not happen according to + PCLTRM 18-17. + + <ESC>E + <ESC>*c720X + <ESC>*c0T + <ESC>*c8.3K +(1) <ESC>%0B /* enter hpgl2/2 */ +(2) <ESC>%0A /* enter pcl */ + <ESC>*c420Y + <ESC>*c0T + <ESC>%1BSP2;PW0;IN;SP6;SC0,100,0,100;PA50,50;SC;SP7;CI450; + <ESC>%1A + <ESC>E + + the two commands (1) and (2) change the behavior the HP scaling + but not Artifex Scaling. If (1) and (2) are removed both HP and + Artifex produce the same results. + +2101, 2102: + + See comments for test 830 and 831. + +2106: + + Logical operations are broken on the CLJ 5/5M. The behavior of the Artifex + PCL 5c interpreter follows the documentation. + +2120, 2122: + + HPGL/2 pixel placement is implemented using the postscript + operator setfilladjust. The HP command definition is not consistant with + the behavior of the implementation and different devices (Color + Laserjet & 6MP) produce different results for each of these test files. + +2210 and 2220 (fourth page): + + SI, SR discrenpancy. + + +2322, 2323: + + Because the Artifex PCL 5c interpreter determines which regions are "white" + for purposes of transparency before taking into account any color lookup + table modifications, the white arrows in the center of these images are + considered transparent even in the center case (the inverting color + lookup table). Hence, for the inverting color lookup table case, the + central rectangle of the raster will be completely white. + +2330: + + The CLJ 5/5M does not support the viewing illuminant command; the Artifex + PCL interpreter does. + +2331: + + These rasters are rendered in a device independent color space, hence + their appearance will be dependent on the color rendering dictionary + provided. + +2351, 2352: + + The driver configuration command linearly maps saturation and + lightness arguments to pcl's gamma function. It is expected that + vendors will provide product specific code for this function. + +2412: + + After downloading a color lookup table, the monochrome palettes at the + bottom of the first and second pages of this test have one additional + black entry when rendered with the Artifex PCL 5c interpreter, as compared + to the output of the CLJ 5/5M. This problem has not been analyzed. + +PCL5c ATS Anomalies +=================== + + +ak506k21.bin: + + A PCL raster does not overlap an HPGL/2 line segment because the + line is not positioned exactly like HP due to a rounding + difference. The HP 1600C/CM also images this differently than + the HP Color Laserjet breaking only half of the line. After + rounding to the nearest pixel the ASI interpreter places the + raster rectangle one 300 dpi pixel below the gl/2 line. The HP + overlaps for at least one pixel on the 1600C/CM and the width of + the line on the Color Laserjet. + +fp309k22.bin: + + The right edge of the clipboard is missing. This is a font + rasterizer anomaly. The clipboard is a winding bitmap font and + images correctly at 600 dpi but is slightly clipped at 300 dpi. + +Qp606w21.bin: + + It is possible for the artifex interpreter to miss closing a + path in polygon mode under certain unusual conditions, due to + rounding problems. Here is a very simple example that + demonstrates the problem. This problem has only manifested in + problems of low visibility so we have not fixed it. + +begin 664 Qp606w21.bin.small +M&R4M,3(S-#580%!*3"!3150@4$%'15!23U1%0U0]05543PI`4$I,(%-%5"!2 +M15-/3%5424]./38P,`I`4$I,($5.5$52($Q!3D=504=%/5!#3`H;11LE,$)) +M3E-0,5!!4%<N-3M053(Q,C`L,SDT-CM033`[4$0[4%(M."PM,BPM-#8L+3$Q +?+#(R,2PM.#8W+"TQ-C<L.#@P.U!-,CM%4!LE,$$;10`` +` +end + + +--- + +HP Color Laserjet 5C FTS printed on the Color Laserjet 4600 + +panel 411 - The HP interpreter falls back to Times Bold Italic on line +6. On the previous line the brush font was properly selected, text +printed with the font then typeface family 4128 is selected. +Extracting out the non vendor bits results in typeface 32 which is the +typeface number of the brush font. There are no intervening relevant +commands before the next sentence is printed so, we don't see how any +other font than brush font could be selected and assume this is a bug +in the HP printer. Similarly we believe the Dom Casual downloaded +font should be selected on lines 7 & 8. + + +---- + +HP Color Laserjet 4600 CET + +18-01.BIN page 25 - The vertical bar and checkerboard character are +missing on this page. The glyphs are not actually present in the +downloaded font. It will work properly with Monotype if the plugins +are configured correctly. + +20-07.BIN page 18 (repeats throughout test) - The HP prints the text +in the wrong color. The logical operation 17 (DSon) is used to paint +green text on a white background. The result should be black, the +text is green. The following example prints the wrong colored text +from the example and a rectangle with the same raster operation and +colors, the rectangle is the predicted black and the text is green. + +(quoted printable) + +=1BE=1B*r3U=1B*v2S=1B*l17O=1B*p300x400Y=1B*c90A=1B*c150B=1B*c0PDownloa= +ding symbol set 62F and making it permanent=1BE + + +24-04 page 3, 4 and 6 - The HP 4600 is incorrect. The reference point is +explicitly set to the current position before drawing the rectangles. +The pattern's origin should coincide with the rectangle's origin as it +does in the Artifex output. + + +28-10 page 11 - This test checks fractional bit support for the +polyline encoding command. The last box on the page uses 26 fractional +bits, Artifex supports this and prints the box, the HP 4600 does not +support 26 bits and does not print the box. The PCL Technical +Reference Manual calls states the -26 <= fractional bits <= 26. The +HPGL/2 RTL tecnical reference manual states the value is device +dependent. + + + +---- + +HP Color Laserjet 4600 CET printed on the Color Laserjet 4550 + + +21-09.BIN : + + 4550 printer infinite loop raster width range test. + + +21-10.BIN : + + 4550 printer infinite loop raster height range test. + + +21-10.BIN page 24, 25 and +21-12.BIN page 17 : + + Raster height > raster sent and the palette +0 entry is not white. We zero fill with white, HP with Black or +the palette color at entry 0. + + +21-12.BIN page 19 : + + HP incorrectly renders the first image stretching it +in the X dimension. + + +21-13.BIN page 2 : + + HP incorrectly renders 4 of the rasters on the page +Black triangles appear in a regular pattern across the raster + + + + |