diff options
Diffstat (limited to 'pngrtran.c')
| -rw-r--r-- | pngrtran.c | 97 |
1 files changed, 52 insertions, 45 deletions
diff --git a/pngrtran.c b/pngrtran.c index a475f9a9a..f9c090be2 100644 --- a/pngrtran.c +++ b/pngrtran.c @@ -1,7 +1,7 @@ /* pngrtran.c - transforms the data in a row for PNG readers * - * Last changed in libpng 1.4.6 [%RDATE%] + * Last changed in libpng 1.4.8 [July 7, 2011] * Copyright (c) 1998-2011 Glenn Randers-Pehrson * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) @@ -660,10 +660,21 @@ void PNGAPI png_set_rgb_to_gray(png_structp png_ptr, int error_action, double red, double green) { - int red_fixed = (int)((float)red*100000.0 + 0.5); - int green_fixed = (int)((float)green*100000.0 + 0.5); + int red_fixed, green_fixed; if (png_ptr == NULL) return; + if (red > 21474.83647 || red < -21474.83648 || + green > 21474.83647 || green < -21474.83648) + { + png_warning(png_ptr, "ignoring out of range rgb_to_gray coefficients"); + red_fixed = -1; + green_fixed = -1; + } + else + { + red_fixed = (int)((float)red*100000.0 + 0.5); + green_fixed = (int)((float)green*100000.0 + 0.5); + } png_set_rgb_to_gray_fixed(png_ptr, error_action, red_fixed, green_fixed); } #endif @@ -703,27 +714,38 @@ png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action, } #endif { - png_uint_16 red_int, green_int; - if (red < 0 || green < 0) - { - red_int = 6968; /* .212671 * 32768 + .5 */ - green_int = 23434; /* .715160 * 32768 + .5 */ - } - else if (red + green < 100000L) + if (red >= 0 && green >= 0 && red + green <= 100000L) { + png_uint_16 red_int, green_int; + red_int = (png_uint_16)(((png_uint_32)red*32768L)/100000L); green_int = (png_uint_16)(((png_uint_32)green*32768L)/100000L); + + png_ptr->rgb_to_gray_red_coeff = red_int; + png_ptr->rgb_to_gray_green_coeff = green_int; + png_ptr->rgb_to_gray_blue_coeff = + (png_uint_16)(32768 - red_int - green_int); } + else { - png_warning(png_ptr, "ignoring out of range rgb_to_gray coefficients"); - red_int = 6968; - green_int = 23434; + if (red >= 0 && green >= 0) + png_warning(png_ptr, + "ignoring out of range rgb_to_gray coefficients"); + + /* Use the defaults, from the cHRM chunk if set, else the built in Rec + * 709 values (which correspond to sRGB, so we don't have to worry + * about the sRGB chunk!) + */ + if (png_ptr->rgb_to_gray_red_coeff == 0 && + png_ptr->rgb_to_gray_green_coeff == 0 && + png_ptr->rgb_to_gray_blue_coeff == 0) + { + png_ptr->rgb_to_gray_red_coeff = 6968; /* .212671 * 32768 + .5 */ + png_ptr->rgb_to_gray_green_coeff = 23434; /* .715160 * 32768 + .5 */ + png_ptr->rgb_to_gray_blue_coeff = 2366; + } } - png_ptr->rgb_to_gray_red_coeff = red_int; - png_ptr->rgb_to_gray_green_coeff = green_int; - png_ptr->rgb_to_gray_blue_coeff = - (png_uint_16)(32768 - red_int - green_int); } } #endif @@ -1181,8 +1203,7 @@ png_read_transform_info(png_structp png_ptr, png_infop info_ptr) { if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE) { - if (png_ptr->num_trans && - (png_ptr->transformations & PNG_EXPAND_tRNS)) + if (png_ptr->num_trans) info_ptr->color_type = PNG_COLOR_TYPE_RGB_ALPHA; else info_ptr->color_type = PNG_COLOR_TYPE_RGB; @@ -1778,32 +1799,18 @@ png_do_chop(png_row_infop row_info, png_bytep row) for (i = 0; i<istop; i++, sp += 2, dp++) { #ifdef PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED - /* This does a more accurate scaling of the 16-bit color - * value, rather than a simple low-byte truncation. - * - * What the ideal calculation should be: - * *dp = (((((png_uint_32)(*sp) << 8) | - * (png_uint_32)(*(sp + 1))) * 255 + 127) - * / (png_uint_32)65535L; - * - * GRR: no, I think this is what it really should be: - * *dp = (((((png_uint_32)(*sp) << 8) | - * (png_uint_32)(*(sp + 1))) + 128L) - * / (png_uint_32)257L; - * - * GRR: here's the exact calculation with shifts: - * temp = (((png_uint_32)(*sp) << 8) | - * (png_uint_32)(*(sp + 1))) + 128L; - * *dp = (temp - (temp >> 8)) >> 8; - * - * Approximate calculation with shift/add instead of multiply/divide: - * *dp = ((((png_uint_32)(*sp) << 8) | - * (png_uint_32)((int)(*(sp + 1)) - *sp)) + 128) >> 8; - * - * What we actually do to avoid extra shifting and conversion: - */ - - *dp = *sp + ((((int)(*(sp + 1)) - *sp) > 128) ? 1 : 0); + /* This does a more accurate scaling of the 16-bit color + * value, rather than a simple low-byte truncation. + * + * Prior to libpng-1.4.8 and 1.5.4, the calculation here was + * incorrect, so if you used ACCURATE_SCALE you will now see + * a slightly different result. In libpng-1.5.4 and + * later you will need to use the new png_set_scale_16_to_8() + * API to obtain accurate 16-to-8 scaling. + */ + png_int_32 tmp = *sp; /* must be signed! */ + tmp += (((int)sp[1] - tmp + 128) * 65535) >> 24; + *dp = (png_byte)tmp; #else /* Simply discard the low order byte */ *dp = *sp; |