Sorry about the comment about unnecessary memory allocation, it's needed,
I confused with the libpng implementation where it's not.
Here is my png encode that produce wrong results.
#if defined(HAVE_LIBPNG) && defined(HAVE_LIBZ)
/* structure to store PNG image bytes */
typedef struct {
uchar *buffer;
size_t size;
size_t size_allocated;
} mem_encode;
void my_png_write_data(png_structp png_ptr, png_bytep data, png_size_t
length){
mem_encode* p=(mem_encode*)png_get_io_ptr(png_ptr);
size_t nsize = p->size + length;
/* allocate or grow buffer */
if(nsize > p->size_allocated){
int alloc_size = nsize * 2;
if(p->buffer)
p->buffer = (uchar*)realloc(p->buffer, alloc_size);
else
p->buffer = (uchar*)malloc(alloc_size);
if(!p->buffer) {
png_error(png_ptr, "Write Error");
return;
}
p->size_allocated = alloc_size;
}
/* copy new bytes to end of buffer */
memcpy(p->buffer + p->size, data, length);
p->size += length;
}
/* This is optional but included to show how png_set_write_fn() is called
*/
void my_png_flush(png_structp png_ptr){}
#endif // HAVE_LIBPNG && HAVE_LIBZ
int Fl_PNG_Image::encode(Fl_Image *img, unsigned char **outbuffer, int
&outlen){
#if defined(HAVE_LIBPNG) && defined(HAVE_LIBZ)
int imgw = img->w(), imgh = img->h(), imgd = img->d();
outlen = imgw * imgh * imgd;
png_structp pp; // PNG data
png_infop info; // PNG image info
mem_encode state;
/* initialise - put this before png_write_png() call */
state.buffer = NULL;
state.size = 0;
state.size_allocated = 0;
if( !((imgd == 1) || (imgd ==3) || (imgd ==4))) return -1;
pp = png_create_write_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
if(!pp) return -1;
info = png_create_info_struct(pp);
if (!info){
png_destroy_write_struct(&pp, 0);
return -1;
}
if (setjmp(png_jmpbuf(pp))){
png_destroy_write_struct(&pp, &info);
return -1;
}
//png_init_io(pp, fp);
/* if my_png_flush() is not needed, change the arg to NULL */
png_set_write_fn(pp, &state, my_png_write_data, my_png_flush);
png_set_compression_level(pp, Z_BEST_COMPRESSION);
png_set_IHDR(pp, info, imgw, imgh, 8,
imgd == 1 ? PNG_COLOR_TYPE_GRAY : PNG_COLOR_TYPE_RGB,
PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT,
PNG_FILTER_TYPE_DEFAULT);
png_set_sRGB(pp, info, PNG_sRGB_INTENT_PERCEPTUAL);
png_set_sRGB_gAMA_and_cHRM(pp, info, PNG_INFO_sRGB);
png_write_info(pp, info);
uchar *idata = (uchar *)img->data()[0];
int iwd = imgw * imgd;
for (int y = 0; y < imgh; y++)
{
png_write_row(pp, (png_byte *)(idata + y * iwd));
}
png_write_end(pp, info);
png_destroy_write_struct(&pp, 0);
/* cleanup */
//if(state.buffer) free(state.buffer);
*outbuffer = state.buffer;
outlen = state.size;
// FILE* outfile = fopen("test.png", "wb");
// if (outfile){
// fwrite(*outbuffer, outlen,1 ,outfile);
// fclose(outfile);
// }
return 0;
#else
return -1;
#endif // HAVEHAVE_LIBPNG && HAVE_LIBZ
}
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