diff options
Diffstat (limited to 'converter/other/pngx.c')
| -rw-r--r-- | converter/other/pngx.c | 72 |
1 files changed, 67 insertions, 5 deletions
diff --git a/converter/other/pngx.c b/converter/other/pngx.c index 185b4a27..4bb09421 100644 --- a/converter/other/pngx.c +++ b/converter/other/pngx.c @@ -1,3 +1,4 @@ +#include <stdbool.h> #include <assert.h> #include <png.h> #include "pm_c_util.h" @@ -59,6 +60,7 @@ pngx_create(struct pngx ** const pngxPP, if (!pngxP) pm_error("Failed to allocate memory for PNG object"); else { + pngxP->infoPrepared = false; pngxP->numPassesRequired = 1; switch(rw) { @@ -347,7 +349,7 @@ void pngx_setChrm(struct pngx * const pngxP, struct pngx_chroma const chroma) { - png_set_cHRM(pngxP->png_ptr, pngxP->info_ptr, + png_set_cHRM(pngxP->png_ptr, pngxP->info_ptr, chroma.wx, chroma.wy, chroma.rx, chroma.ry, chroma.gx, chroma.gy, @@ -466,6 +468,37 @@ pngx_setIhdr(struct pngx * const pngxP, void pngx_setInterlaceHandling(struct pngx * const pngxP) { + /* The documentation is vague and contradictory on what this does, but + what it appears from reasoning and experimentation to do is the + following. + + It applies to reading and writing by rows (png_write_row, png_read_row) + as opposed to whole image (png_write_image, png_read_image). It has + no effect on whole image read and write. + + This is not what makes an image interlaced or tells the decompressor + that it is interlaced. All it does is control how you you read and + write the raster when the image is interlaced. It has no effect if the + image is not interlaced. (You make an image interlaced by setting the + IHDR; the decompressor finds out from the IHDR that it is interlaced). + + In the write case, it controls whether you construct the subimages + yourself and feed them to libpng in sequence or you feed libpng the + entire image multiple times and libpng picks out the pixels appropriate + for each subimage in each pass. + + In the read case, it controls whether you get the raw subimages and you + assemble them into the full image or you read the whole image multiple + times into the same buffer, with the pixels that belong to each + subimage being filled in on each pass. + + Note that the only kind of interlacing that exists today is ADAM7 and + consequently, the number of passes is always 1 (for no interlacing) or + 7 (for interlacing). + */ + if (!pngxP->infoPrepared) + pm_error("pngx_setInterlaceHandling must not be called before " + "pngx_writeInfo or pngx_readInfo"); pngxP->numPassesRequired = png_set_interlace_handling(pngxP->png_ptr); } @@ -475,6 +508,10 @@ pngx_setInterlaceHandling(struct pngx * const pngxP) { void pngx_setPacking(struct pngx * const pngxP) { + if (!pngxP->infoPrepared) + pm_error("pngx_setPacking must not be called before " + "pngx_writeInfo or pngx_readInfo"); + png_set_packing(pngxP->png_ptr); } @@ -484,7 +521,7 @@ void pngx_setPhys(struct pngx * const pngxP, struct pngx_phys const phys) { - png_set_pHYs(pngxP->png_ptr, pngxP->info_ptr, + png_set_pHYs(pngxP->png_ptr, pngxP->info_ptr, phys.x, phys.y, phys.unit); } @@ -516,7 +553,19 @@ pngx_setSbit(struct pngx * const pngxP, void pngx_setShift(struct pngx * const pngxP, png_color_8 const sigBitArg) { - +/*---------------------------------------------------------------------------- + Tell the number of significant bits in the row buffers that will be given + to the compressor. Those bits are the least significant of the 8 bits of + space in the row buffer for each sample. For example, if red sample values + are in the range 0-7, only the lower 3 bits of the 8-bit byte for each + red sample will be used, so one would call this with sigBitArg.red == 3. + + The name alludes to the fact that to normalize the sample to 8 bits, one + shifts it left, and this function tells how much shift has to happen. In + the example above, each red sample has to be shifted left 5 bits (so that + the upper 3 bits are significant and the lower 5 bits are always zero) to + create an 8 bit sample out of the 3 bit samples. +-----------------------------------------------------------------------------*/ png_color_8 sigBit; sigBit = sigBitArg; @@ -651,6 +700,8 @@ void pngx_readInfo(struct pngx * const pngxP) { png_read_info(pngxP->png_ptr, pngxP->info_ptr); + + pngxP->infoPrepared = true; } @@ -659,6 +710,8 @@ void pngx_writeInfo(struct pngx * const pngxP) { png_write_info(pngxP->png_ptr, pngxP->info_ptr); + + pngxP->infoPrepared = true; } @@ -688,7 +741,7 @@ pngx_readStart(struct pngx * const pngxP, FILE * const ifP) { size_t sigByteCt; - + verifyFileIsPng(ifP, &sigByteCt); /* Declare that we already read the signature bytes */ @@ -733,9 +786,18 @@ pngx_writeRow(struct pngx * const pngxP, void +pngx_writeImage(struct pngx * const pngxP, + png_byte ** const raster) { + + png_write_image(pngxP->png_ptr, (png_byte **)raster); +} + + + +void pngx_readEnd(struct pngx * const pngxP) { - /* Note that some of info_ptr is not defined until png_read_end() + /* Note that some of info_ptr is not defined until png_read_end() completes. That's because it comes from chunks that are at the end of the stream. In particular, text and time chunks may be at the end. Furthermore, they may be in both places, in |