png_set_IHDR(png_ptr, info_ptr, width, height, 8, PNG_COLOR_TYPE_RGB_ALPHA,
PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
/* set the palette if there is one. REQUIRED for indexed-color images */
palette = (png_colorp)png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH
* sizeof (png_color));
/* ... set palette colors ... */
png_set_PLTE(png_ptr, info_ptr, palette, PNG_MAX_PALETTE_LENGTH);
/* You must not free palette here, because png_set_PLTE only makes a link to
the palette that you malloced. Wait until you are about to destroy
the png structure. */
just remove the last 2 calls?