Add an API to import a color-mapped image.

Change-Id: I71421a1a706a74d184a24dc9276b55005d7457b5

extras/extras.c

@@ -11,7 +11,9 @@
 //
 
 #include "./extras.h"
+#include "webp/format_constants.h"
 
+#include <assert.h>
 #include <string.h>
 
 #define XTRA_MAJ_VERSION 0
@@ -108,4 +110,33 @@ int WebPImportRGB4444(const uint8_t* rgb4444, WebPPicture* pic) {
   return 1;
 }
 
+int WebPImportColorMappedARGB(const uint8_t* indexed, int indexed_stride,
+                              const uint32_t palette[], int palette_size,
+                              WebPPicture* pic) {
+  int x, y;
+  uint32_t* dst;
+  // 256 as the input buffer is uint8_t.
+  assert(MAX_PALETTE_SIZE <= 256);
+  if (pic == NULL || indexed == NULL || indexed_stride < pic->width ||
+      palette == NULL || palette_size > MAX_PALETTE_SIZE || palette_size <= 0) {
+    return 0;
+  }
+  pic->use_argb = 1;
+  if (!WebPPictureAlloc(pic)) return 0;
+  dst = pic->argb;
+  for (y = 0; y < pic->height; ++y) {
+    for (x = 0; x < pic->width; ++x) {
+      // Make sure we are within the palette.
+      if (indexed[x] >= palette_size) {
+        WebPPictureFree(pic);
+        return 0;
+      }
+      dst[x] = palette[indexed[x]];
+    }
+    indexed += indexed_stride;
+    dst += pic->argb_stride;
+  }
+  return 1;
+}
+
 //------------------------------------------------------------------------------

extras/extras.h

@@ -42,6 +42,15 @@ WEBP_EXTERN(int) WebPImportRGB565(const uint8_t* rgb565, WebPPicture* pic);
 // width and height must be set prior to calling this function.
 WEBP_EXTERN(int) WebPImportRGB4444(const uint8_t* rgb4444, WebPPicture* pic);
 
+// Import a color mapped image. The number of colors is less or equal to
+// MAX_PALETTE_SIZE. 'pic' must have been initialized. Its content, if any,
+// will be discarded. Returns 'false' in case of error, or if indexed[] contains
+// invalid indices.
+WEBP_EXTERN(int)
+WebPImportColorMappedARGB(const uint8_t* indexed, int indexed_stride,
+                          const uint32_t palette[], int palette_size,
+                          WebPPicture* pic);
+
 //------------------------------------------------------------------------------
 
 // Parse a bitstream, search for VP8 (lossy) header and report a