PNG reader: implement loading HDR image as SDR (#971)

strukturag · Oct 18, 2023 · b051d31 · b051d31
1 parent f4f185b
commit b051d31
Showing 1 changed file with 40 additions and 14 deletions.
diff --git a/examples/decoder_png.cc b/examples/decoder_png.cc
@@ -352,12 +352,22 @@ InputImage loadPNG(const char* filename, int output_bit_depth)
     }
   }
   else {
-    err = heif_image_create((int) width, (int) height,
-                            heif_colorspace_RGB,
-                            has_alpha ?
-                            heif_chroma_interleaved_RRGGBBAA_LE :
-                            heif_chroma_interleaved_RRGGBB_LE,
-                            &image);
+    if (output_bit_depth == 8) {
+      err = heif_image_create((int) width, (int) height,
+                              heif_colorspace_RGB,
+                              has_alpha ?
+                              heif_chroma_interleaved_RGBA :
+                              heif_chroma_interleaved_RGB,
+                              &image);
+    }
+    else {
+      err = heif_image_create((int) width, (int) height,
+                              heif_colorspace_RGB,
+                              has_alpha ?
+                              heif_chroma_interleaved_RRGGBBAA_LE :
+                              heif_chroma_interleaved_RRGGBB_LE,
+                              &image);
+    }
     (void) err;
 
     int bdShift = 16 - output_bit_depth;
@@ -367,16 +377,32 @@ InputImage loadPNG(const char* filename, int output_bit_depth)
     int stride;
     uint8_t* p_out = (uint8_t*) heif_image_get_plane(image, heif_channel_interleaved, &stride);
 
-    for (uint32_t y = 0; y < height; y++) {
-      uint8_t* p = row_pointers[y];
+    if (output_bit_depth==8) {
+      // convert HDR to SDR
+
+      for (uint32_t y = 0; y < height; y++) {
+        uint8_t* p = row_pointers[y];
 
-      uint32_t nVal = (has_alpha ? 4 : 3) * width;
+        uint32_t nVal = (has_alpha ? 4 : 3) * width;
 
-      for (uint32_t x = 0; x < nVal; x++) {
-        uint16_t v = (uint16_t) (((p[0] << 8) | p[1]) >> bdShift);
-        p_out[2 * x + y * stride + 1] = (uint8_t) (v >> 8);
-        p_out[2 * x + y * stride + 0] = (uint8_t) (v & 0xFF);
-        p += 2;
+        for (uint32_t x = 0; x < nVal; x++) {
+          p_out[x + y * stride] = p[0];
+          p+=2;
+        }
+      }
+    }
+    else {
+      for (uint32_t y = 0; y < height; y++) {
+        uint8_t* p = row_pointers[y];
+
+        uint32_t nVal = (has_alpha ? 4 : 3) * width;
+
+        for (uint32_t x = 0; x < nVal; x++) {
+          uint16_t v = (uint16_t) (((p[0] << 8) | p[1]) >> bdShift);
+          p_out[2 * x + y * stride + 1] = (uint8_t) (v >> 8);
+          p_out[2 * x + y * stride + 0] = (uint8_t) (v & 0xFF);
+          p += 2;
+        }
       }
     }
   }