diff options
Diffstat (limited to 'packages/base/pasjpeg/rdjpgcom.pas')
| -rw-r--r-- | packages/base/pasjpeg/rdjpgcom.pas | 381 |
1 files changed, 0 insertions, 381 deletions
diff --git a/packages/base/pasjpeg/rdjpgcom.pas b/packages/base/pasjpeg/rdjpgcom.pas deleted file mode 100644 index bbecb18752..0000000000 --- a/packages/base/pasjpeg/rdjpgcom.pas +++ /dev/null @@ -1,381 +0,0 @@ -Program rdjpgcom; - -{ This file contains a very simple stand-alone application that displays - the text in COM (comment) markers in a JFIF file. - This may be useful as an example of the minimum logic needed to parse - JPEG markers. } - -{ Original: Copyright (C) 1994-1995, Thomas G. Lane. } -uses - Objects; - -const - EXIT_FAILURE = 1; - EXIT_SUCCESS = 0; -type - int = integer; - uInt = word; - -{ These macros are used to read the input file. - To reuse this code in another application, you might need to change these. } - -var - infile : TBufStream; { input JPEG file } - -{ Return next input byte, or EOF if no more } - -function NEXTBYTE : byte; -var - c : Byte; -begin - infile.Read(c, 1); - NEXTBYTE := c; -end; - -{ Error exit handler } -procedure ERREXIT(msg : string); -begin - WriteLn(output, msg); - Halt(EXIT_FAILURE); -end; - - -{ Read one byte, testing for EOF } -function read_1_byte : int; -var - c : int; -begin - c := NEXTBYTE; - if (infile.Status <> stOK) then - ERREXIT('Premature EOF in JPEG file'); - read_1_byte := c; -end; - -{ Read 2 bytes, convert to unsigned int } -{ All 2-byte quantities in JPEG markers are MSB first } -function read_2_bytes : uInt; -var - c : word; -begin - infile.Read(c, 2); - c := Swap(c); - if (infile.Status <> stOK) then - ERREXIT('Premature EOF in JPEG file'); - read_2_bytes := c; -end; - - -{ JPEG markers consist of one or more 0xFF bytes, followed by a marker - code byte (which is not an FF). Here are the marker codes of interest - in this program. (See jdmarker.c for a more complete list.) } - -const - M_SOF0 = $C0; { Start Of Frame N } - M_SOF1 = $C1; { N indicates which compression process } - M_SOF2 = $C2; { Only SOF0-SOF2 are now in common use } - M_SOF3 = $C3; - M_SOF5 = $C5; { NB: codes C4 and CC are NOT SOF markers } - M_SOF6 = $C6; - M_SOF7 = $C7; - M_SOF9 = $C9; - M_SOF10 = $CA; - M_SOF11 = $CB; - M_SOF13 = $CD; - M_SOF14 = $CE; - M_SOF15 = $CF; - M_SOI = $D8; { Start Of Image (beginning of datastream) } - M_EOI = $D9; { End Of Image (end of datastream) } - M_SOS = $DA; { Start Of Scan (begins compressed data) } - M_COM = $FE; { COMment } - - -{ Find the next JPEG marker and return its marker code. - We expect at least one FF byte, possibly more if the compressor used FFs - to pad the file. - There could also be non-FF garbage between markers. The treatment of such - garbage is unspecified; we choose to skip over it but emit a warning msg. - NB: this routine must not be used after seeing SOS marker, since it will - not deal correctly with FF/00 sequences in the compressed image data... } - -function next_marker : int; -var - c : int; - discarded_bytes : int; -begin - discarded_bytes := 0; - - { Find 0xFF byte; count and skip any non-FFs. } - c := read_1_byte; - while (c <> $FF) do - begin - Inc(discarded_bytes); - c := read_1_byte; - end; - { Get marker code byte, swallowing any duplicate FF bytes. Extra FFs - are legal as pad bytes, so don't count them in discarded_bytes. } - - repeat - c := read_1_byte; - until (c <> $FF); - - if (discarded_bytes <> 0) then - begin - WriteLn(output, 'Warning: garbage data found in JPEG file'); - end; - - next_marker := c; -end; - - -{ Read the initial marker, which should be SOI. - For a JFIF file, the first two bytes of the file should be literally - $FF M_SOI. To be more general, we could use next_marker, but if the - input file weren't actually JPEG at all, next_marker might read the whole - file and then return a misleading error message... } - -function first_marker : int; -var - c1, c2 : int; -begin - c1 := NEXTBYTE; - c2 := NEXTBYTE; - if (c1 <> $FF) or (c2 <> M_SOI) then - ERREXIT('Not a JPEG file'); - first_marker := c2; -end; - - -{ Most types of marker are followed by a variable-length parameter segment. - This routine skips over the parameters for any marker we don't otherwise - want to process. - Note that we MUST skip the parameter segment explicitly in order not to - be fooled by $FF bytes that might appear within the parameter segment; - such bytes do NOT introduce new markers. } - -procedure skip_variable; -{ Skip over an unknown or uninteresting variable-length marker } -var - length : uInt; -begin - { Get the marker parameter length count } - length := read_2_bytes; - { Length includes itself, so must be at least 2 } - if (length < 2) then - ERREXIT('Erroneous JPEG marker length'); - Dec(length, 2); - { Skip over the remaining bytes } - while (length > 0) do - begin - read_1_byte; - Dec(length); - end; -end; - - -{ Process a COM marker. - We want to print out the marker contents as legible text; - we must guard against random junk and varying newline representations. } - -procedure process_COM; -const - CR = 13; - LF = 10; -var - length : uInt; - comment : string; - lastch : byte; -begin - comment := ''; - { Get the marker parameter length count } - length := read_2_bytes; - { Length includes itself, so must be at least 2 } - if (length < 2) then - ERREXIT('Erroneous JPEG marker length'); - Dec(length, 2); - - comment := ''; - while (length > 0) do - begin - comment := comment + char(read_1_byte); - Dec(length); - end; - WriteLn(comment); -end; - - -{ Process a SOFn marker. - This code is only needed if you want to know the image dimensions... } - -procedure process_SOFn (marker : int); -var - length : uInt; - image_height, image_width : uInt; - data_precision, num_components : int; - process : string; - ci: int; -begin - length := read_2_bytes; { usual parameter length count } - - data_precision := read_1_byte; - image_height := read_2_bytes; - image_width := read_2_bytes; - num_components := read_1_byte; - - case marker of - M_SOF0: process := 'Baseline'; - M_SOF1: process := 'Extended sequential'; - M_SOF2: process := 'Progressive'; - M_SOF3: process := 'Lossless'; - M_SOF5: process := 'Differential sequential'; - M_SOF6: process := 'Differential progressive'; - M_SOF7: process := 'Differential lossless'; - M_SOF9: process := 'Extended sequential, arithmetic coding'; - M_SOF10: process := 'Progressive, arithmetic coding'; - M_SOF11: process := 'Lossless, arithmetic coding'; - M_SOF13: process := 'Differential sequential, arithmetic coding'; - M_SOF14: process := 'Differential progressive, arithmetic coding'; - M_SOF15: process := 'Differential lossless, arithmetic coding'; - else - process := 'Unknown'; - end; - - WriteLn('JPEG image is ',image_width,'w * ',image_height,'h, ', - num_components, ' color components, ',data_precision, - ' bits per sample'); - WriteLn('JPEG process: ', process); - - if (length <> uInt(8 + num_components * 3)) then - ERREXIT('Bogus SOF marker length'); - - for ci := 0 to pred(num_components) do - begin - read_1_byte; { Component ID code } - read_1_byte; { H, V sampling factors } - read_1_byte; { Quantization table number } - end; -end; - - -{ Parse the marker stream until SOS or EOI is seen; - display any COM markers. - While the companion program wrjpgcom will always insert COM markers before - SOFn, other implementations might not, so we scan to SOS before stopping. - If we were only interested in the image dimensions, we would stop at SOFn. - (Conversely, if we only cared about COM markers, there would be no need - for special code to handle SOFn; we could treat it like other markers.) } - -function scan_JPEG_header (verbose : boolean) : int; -var - marker : int; -begin - { Expect SOI at start of file } - if (first_marker <> M_SOI) then - ERREXIT('Expected SOI marker first'); - - { Scan miscellaneous markers until we reach SOS. } - repeat - marker := next_marker; - case marker of - M_SOF0, { Baseline } - M_SOF1, { Extended sequential, Huffman } - M_SOF2, { Progressive, Huffman } - M_SOF3, { Lossless, Huffman } - M_SOF5, { Differential sequential, Huffman } - M_SOF6, { Differential progressive, Huffman } - M_SOF7, { Differential lossless, Huffman } - M_SOF9, { Extended sequential, arithmetic } - M_SOF10, { Progressive, arithmetic } - M_SOF11, { Lossless, arithmetic } - M_SOF13, { Differential sequential, arithmetic } - M_SOF14, { Differential progressive, arithmetic } - M_SOF15: { Differential lossless, arithmetic } - if (verbose) then - process_SOFn(marker) - else - skip_variable; - - M_SOS: { stop before hitting compressed data } - begin - scan_JPEG_header := marker; - exit; - end; - - M_EOI: { in case it's a tables-only JPEG stream } - begin - scan_JPEG_header := marker; - exit; - end; - - M_COM: - process_COM; - - else { Anything else just gets skipped } - skip_variable; { we assume it has a parameter count... } - end; - until false; { end loop } -end; - - -{ Command line parsing code } - -var - progname : string[79]; { program name for error messages } - - -procedure usage; -{ complain about bad command line } -begin - WriteLn(output, 'rdjpgcom displays any textual comments in a JPEG file.'); - - WriteLn(output, 'Usage: ',progname,' [switches] [inputfile]'); - - WriteLn(output, 'Switches (names may be abbreviated):'); - WriteLn(output, ' -verbose Also display dimensions of JPEG image'); - - Halt(EXIT_FAILURE); -end; - - -{ The main program. } - -var - verbose : boolean; - argn : int; - arg : string; -begin - verbose := FALSE; - - progname := ParamStr(0); - if (progname = '') then - progname := 'rdjpgcom'; { in case C library doesn't provide it } - - { Parse switches, if any } - for argn := 1 to Pred(ParamCount) do - begin - arg := ParamStr(argn); - if arg[1] = '-' then - if (Pos(arg, '-verbose') > 0) then - begin - verbose := TRUE; - end - else - usage; - end; - - { Open the input file. } - arg := ParamStr(ParamCount); - - if not infile.Init(arg, stOpenRead, 4096) then - begin - WriteLn(output, 'can''t open ', arg); - Halt(EXIT_FAILURE); - end; - - { Scan the JPEG headers. } - scan_JPEG_header(verbose); - - infile.done; - - { All done. } - Halt(EXIT_SUCCESS); -end. |