Function stbi__create_png_image_raw

include/stb/stb_image.h:4696–4859

create the png data from post-deflated data

// create the png data from post-deflated data
static int stbi__create_png_image_raw(stbi__png *a, stbi_uc *raw, stbi__uint32 raw_len, int out_n, stbi__uint32 x, stbi__uint32 y, int depth, int color)
{
   int bytes = (depth == 16 ? 2 : 1);
   stbi__context *s = a->s;
   stbi__uint32 i,j,stride = x*out_n*bytes;
   stbi__uint32 img_len, img_width_bytes;
   stbi_uc *filter_buf;
   int all_ok = 1;
   int k;
   int img_n = s->img_n; // copy it into a local for later

   int output_bytes = out_n*bytes;
   int filter_bytes = img_n*bytes;
   int width = x;

   STBI_ASSERT(out_n == s->img_n || out_n == s->img_n+1);
   a->out = (stbi_uc *) stbi__malloc_mad3(x, y, output_bytes, 0); // extra bytes to write off the end into
   if (!a->out) return stbi__err("outofmem", "Out of memory");

   // note: error exits here don't need to clean up a->out individually,
   // stbi__do_png always does on error.
   if (!stbi__mad3sizes_valid(img_n, x, depth, 7)) return stbi__err("too large", "Corrupt PNG");
   img_width_bytes = (((img_n * x * depth) + 7) >> 3);
   if (!stbi__mad2sizes_valid(img_width_bytes, y, img_width_bytes)) return stbi__err("too large", "Corrupt PNG");
   img_len = (img_width_bytes + 1) * y;

   // we used to check for exact match between raw_len and img_len on non-interlaced PNGs,
   // but issue #276 reported a PNG in the wild that had extra data at the end (all zeros),
   // so just check for raw_len < img_len always.
   if (raw_len < img_len) return stbi__err("not enough pixels","Corrupt PNG");

   // Allocate two scan lines worth of filter workspace buffer.
   filter_buf = (stbi_uc *) stbi__malloc_mad2(img_width_bytes, 2, 0);
   if (!filter_buf) return stbi__err("outofmem", "Out of memory");

   // Filtering for low-bit-depth images
   if (depth < 8) {
      filter_bytes = 1;
      width = img_width_bytes;
   }

   for (j=0; j < y; ++j) {
      // cur/prior filter buffers alternate
      stbi_uc *cur = filter_buf + (j & 1)*img_width_bytes;
      stbi_uc *prior = filter_buf + (~j & 1)*img_width_bytes;
      stbi_uc *dest = a->out + stride*j;
      int nk = width * filter_bytes;
      int filter = *raw++;

      // check filter type
      if (filter > 4) {
         all_ok = stbi__err("invalid filter","Corrupt PNG");
         break;
      }

      // if first row, use special filter that doesn't sample previous row
      if (j == 0) filter = first_row_filter[filter];