diff options
Diffstat (limited to 'converter/other/pamtopng.c')
| -rw-r--r-- | converter/other/pamtopng.c | 99 |
1 files changed, 78 insertions, 21 deletions
diff --git a/converter/other/pamtopng.c b/converter/other/pamtopng.c index 528184b2..fdeb6582 100644 --- a/converter/other/pamtopng.c +++ b/converter/other/pamtopng.c @@ -345,6 +345,60 @@ parseAndScaleColor(const char * const colorString, +static png_color_8 +sigBitsFmImgType(unsigned int const pnmBitDepth, + int const pngColorType) { +/*---------------------------------------------------------------------------- + A representation used in PNG of color resolutions in an original image. +-----------------------------------------------------------------------------*/ + png_color_8 retval; + + /* Initial values */ + if (pnmBitDepth < 8) { + switch (pngColorType) { + case PNG_COLOR_TYPE_RGB: + retval.red = pnmBitDepth; + retval.green = pnmBitDepth; + retval.blue = pnmBitDepth; + retval.gray = 0; + retval.alpha = 0; + break; + case PNG_COLOR_TYPE_RGB_ALPHA: + retval.red = pnmBitDepth; + retval.green = pnmBitDepth; + retval.blue = pnmBitDepth; + retval.gray = 0; + retval.alpha = pnmBitDepth; + break; + case PNG_COLOR_TYPE_GRAY: + /* PNG can (so presumably will) use original bit depth */ + retval.red = 0; + retval.green = 0; + retval.blue = 0; + retval.gray = 0; + retval.alpha = 0; + break; + case PNG_COLOR_TYPE_GRAY_ALPHA: + retval.red = 0; + retval.green = 0; + retval.blue = 0; + retval.gray = pnmBitDepth; + retval.alpha = pnmBitDepth; + break; + } + } else { + /* PNG can (so presumably will) use original bit depth */ + retval.red = 0; + retval.green = 0; + retval.blue = 0; + retval.gray = 0; + retval.alpha = 0; + } + return retval; +} + + + static void doTrnsChunk(const struct pam * const pamP, struct pngx * const pngxP, @@ -411,27 +465,12 @@ doGamaChunk(struct pngx * const pngxP, static void doSbitChunk(const struct pam * const pamP, - struct pngx * const pngxP) { - - unsigned int const pnmBitDepth = pm_maxvaltobits(pamP->maxval); + struct pngx * const pngxP, + png_color_8 const sigBits) { - /* create SBIT chunk in case of 1,2,4 bit deep images stored in 8 bit - format PNG files - */ - if (pngx_colorType(pngxP) != PNG_COLOR_TYPE_GRAY && pnmBitDepth < 8) { - png_color_8 sBit; - - if (pngx_colorType(pngxP) == PNG_COLOR_TYPE_RGB || - pngx_colorType(pngxP) == PNG_COLOR_TYPE_RGB_ALPHA) { - sBit.red = sBit.green = sBit.blue = pnmBitDepth; - } else { - sBit.gray = pnmBitDepth; - } - if (pngx_colorType(pngxP) == PNG_COLOR_TYPE_RGB_ALPHA || - pngx_colorType(pngxP) == PNG_COLOR_TYPE_GRAY_ALPHA) { - sBit.alpha = pnmBitDepth; - } - pngx_setSbit(pngxP, sBit); + if (sigBits.red + sigBits.green + sigBits.blue + + sigBits.gray + sigBits.alpha > 0) { + pngx_setSbit(pngxP, sigBits); } } @@ -552,6 +591,20 @@ doTimeChunk(struct pngx * const pngxP, static void +setShift(struct pngx * const pngxP, + png_color_8 const sigBits) { + + if (sigBits.red + sigBits.green + sigBits.blue + + sigBits.gray + sigBits.alpha > 0) { + + /* Move the 1, 2, 4 bits to most significant bits */ + pngx_setShift(pngxP, sigBits); + } +} + + + +static void convertRaster(const struct pam * const pamP, const tuple * const tuplerow, png_byte * const pngRow, @@ -648,6 +701,8 @@ writePng(const struct pam * const pamP, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE); + sBit = sigBitsFmImgType(pnmBitDepth, pngColorType); + /* Where requested, add ancillary chunks */ if (cmdline.transparencySpec) doTrnsChunk(pamP, pngxP,cmdline.transparency); @@ -660,7 +715,7 @@ writePng(const struct pam * const pamP, /* no iccp */ - doSbitChunk(pamP, pngxP); + doSbitChunk(pamP, pngxP, sBit); if (cmdline.srgbintentSpec) doSrgbChunk(pngxP, cmdline.srgbintent); @@ -686,6 +741,8 @@ writePng(const struct pam * const pamP, if (cmdline.timeSpec) doTimeChunk(pngxP, cmdline.time); + setShift(pngxP, sBit); + /* Write the ancillary chunks to PNG file */ pngx_writeInfo(pngxP); |