add missing WebPDecodeARGBInto() and switch ARGB4444 to RGBA4444 as was intended

src/dec/io.c

@@ -99,13 +99,13 @@ UPSAMPLE_FUNC(UpsampleBgrLinePair,  VP8YuvToBgr,  3)
 UPSAMPLE_FUNC(UpsampleRgbaLinePair, VP8YuvToRgba, 4)
 UPSAMPLE_FUNC(UpsampleBgraLinePair, VP8YuvToBgra, 4)
 UPSAMPLE_FUNC(UpsampleArgbLinePair, VP8YuvToArgb, 4)
-UPSAMPLE_FUNC(UpsampleArgb4444LinePair, VP8YuvToArgb4444, 2)
+UPSAMPLE_FUNC(UpsampleRgba4444LinePair, VP8YuvToRgba4444, 2)
 UPSAMPLE_FUNC(UpsampleRgb565LinePair,  VP8YuvToRgb565,  2)
 // These two don't erase the alpha value
 UPSAMPLE_FUNC(UpsampleRgbKeepAlphaLinePair, VP8YuvToRgb, 4)
 UPSAMPLE_FUNC(UpsampleBgrKeepAlphaLinePair, VP8YuvToBgr, 4)
 UPSAMPLE_FUNC(UpsampleArgbKeepAlphaLinePair, VP8YuvToArgbKeepA, 4)
-UPSAMPLE_FUNC(UpsampleArgb4444KeepAlphaLinePair, VP8YuvToArgb4444KeepA, 2)
+UPSAMPLE_FUNC(UpsampleRgba4444KeepAlphaLinePair, VP8YuvToRgba4444KeepA, 2)
 
 #undef LOAD_UV
 #undef UPSAMPLE_FUNC
@@ -120,7 +120,7 @@ static void InitUpsamplers(void) {
   WebPUpsamplers[MODE_BGR]       = UpsampleBgrLinePair;
   WebPUpsamplers[MODE_BGRA]      = UpsampleBgraLinePair;
   WebPUpsamplers[MODE_ARGB]      = UpsampleArgbLinePair;
-  WebPUpsamplers[MODE_ARGB_4444] = UpsampleArgb4444LinePair;
+  WebPUpsamplers[MODE_RGBA_4444] = UpsampleRgba4444LinePair;
   WebPUpsamplers[MODE_RGB_565]   = UpsampleRgb565LinePair;
 
   WebPUpsamplersKeepAlpha[MODE_RGB]       = UpsampleRgbLinePair;
@@ -128,7 +128,7 @@ static void InitUpsamplers(void) {
   WebPUpsamplersKeepAlpha[MODE_BGR]       = UpsampleBgrLinePair;
   WebPUpsamplersKeepAlpha[MODE_BGRA]      = UpsampleBgrKeepAlphaLinePair;
   WebPUpsamplersKeepAlpha[MODE_ARGB]      = UpsampleArgbKeepAlphaLinePair;
-  WebPUpsamplersKeepAlpha[MODE_ARGB_4444] = UpsampleArgb4444KeepAlphaLinePair;
+  WebPUpsamplersKeepAlpha[MODE_RGBA_4444] = UpsampleRgba4444KeepAlphaLinePair;
   WebPUpsamplersKeepAlpha[MODE_RGB_565]   = UpsampleRgb565LinePair;
 
   // If defined, use CPUInfo() to overwrite some pointers with faster versions.
@@ -175,7 +175,7 @@ SAMPLE_FUNC(SampleBgrLinePair,      VP8YuvToBgr,  3)
 SAMPLE_FUNC(SampleRgbaLinePair,     VP8YuvToRgba, 4)
 SAMPLE_FUNC(SampleBgraLinePair,     VP8YuvToBgra, 4)
 SAMPLE_FUNC(SampleArgbLinePair,     VP8YuvToArgb, 4)
-SAMPLE_FUNC(SampleArgb4444LinePair, VP8YuvToArgb4444, 2)
+SAMPLE_FUNC(SampleRgba4444LinePair, VP8YuvToRgba4444, 2)
 SAMPLE_FUNC(SampleRgb565LinePair,   VP8YuvToRgb565, 2)
 
 #undef SAMPLE_FUNC
@@ -192,7 +192,7 @@ static const SampleLinePairFunc kSamplers[MODE_LAST] = {
   SampleBgrLinePair,       // MODE_BGR
   SampleBgraLinePair,      // MODE_BGRA
   SampleArgbLinePair,      // MODE_ARGB
-  SampleArgb4444LinePair,  // MODE_ARGB_4444
+  SampleRgba4444LinePair,  // MODE_RGBA_4444
   SampleRgb565LinePair     // MODE_RGB_565
 };
 
@@ -211,7 +211,7 @@ YUV444_FUNC(Yuv444ToBgr,      VP8YuvToBgr,  3)
 YUV444_FUNC(Yuv444ToRgba,     VP8YuvToRgba, 4)
 YUV444_FUNC(Yuv444ToBgra,     VP8YuvToBgra, 4)
 YUV444_FUNC(Yuv444ToArgb,     VP8YuvToArgb, 4)
-YUV444_FUNC(Yuv444ToArgb4444, VP8YuvToArgb4444, 2)
+YUV444_FUNC(Yuv444ToRgba4444, VP8YuvToRgba4444, 2)
 YUV444_FUNC(Yuv444ToRgb565,   VP8YuvToRgb565, 2)
 
 #undef YUV444_FUNC
@@ -225,7 +225,7 @@ static const YUV444Func kYUV444Converters[MODE_LAST] = {
   Yuv444ToBgr,       // MODE_BGR
   Yuv444ToBgra,      // MODE_BGRA
   Yuv444ToArgb,      // MODE_ARGB
-  Yuv444ToArgb4444,  // MODE_ARGB_4444
+  Yuv444ToRgba4444,  // MODE_RGBA_4444
   Yuv444ToRgb565     // MODE_RGB_565
 };
 
@@ -539,7 +539,7 @@ static int EmitRescaledAlphaYUV(const VP8Io* const io, WebPDecParams* const p) {
 
 static int IsAlphaMode(WEBP_CSP_MODE mode) {
   return (mode == MODE_RGBA || mode == MODE_BGRA || mode == MODE_ARGB ||
-          mode == MODE_ARGB_4444 || mode == MODE_YUVA);
+          mode == MODE_RGBA_4444 || mode == MODE_YUVA);
 }
 
 static int InitYUVRescaler(const VP8Io* const io, WebPDecParams* const p) {

src/dec/webp.c

@@ -146,6 +146,11 @@ uint8_t* WebPDecodeRGBAInto(const uint8_t* data, uint32_t data_size,
   return DecodeIntoRGBABuffer(MODE_RGBA, data, data_size, output, stride, size);
 }
 
+uint8_t* WebPDecodeARGBInto(const uint8_t* data, uint32_t data_size,
+                            uint8_t* output, int size, int stride) {
+  return DecodeIntoRGBABuffer(MODE_ARGB, data, data_size, output, stride, size);
+}
+
 uint8_t* WebPDecodeBGRInto(const uint8_t* data, uint32_t data_size,
                            uint8_t* output, int size, int stride) {
   return DecodeIntoRGBABuffer(MODE_BGR, data, data_size, output, stride, size);

src/dec/yuv.h

@@ -60,21 +60,21 @@ static inline void VP8YuvToArgb(uint8_t y, uint8_t u, uint8_t v,
   VP8YuvToArgbKeepA(y, u, v, argb);
 }
 
-static inline void VP8YuvToArgb4444KeepA(uint8_t y, uint8_t u, uint8_t v,
+static inline void VP8YuvToRgba4444KeepA(uint8_t y, uint8_t u, uint8_t v,
                                          uint8_t* const argb) {
   const int r_off = VP8kVToR[v];
   const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX;
   const int b_off = VP8kUToB[u];
-  // Don't update Aplha (first 4 bits of argb[0])
-  argb[0] = VP8kClip4Bits[y + r_off - YUV_RANGE_MIN];
-  argb[1] = ((VP8kClip[y + g_off - YUV_RANGE_MIN] & 0xf0) |
-             VP8kClip4Bits[y + b_off - YUV_RANGE_MIN]);
+  // Don't update Aplha (last 4 bits of argb[1])
+  argb[0] = ((VP8kClip4Bits[y + r_off - YUV_RANGE_MIN] << 4) |
+             VP8kClip4Bits[y + g_off - YUV_RANGE_MIN]);
+  argb[1] = (argb[1] & 0x0f) | (VP8kClip4Bits[y + b_off - YUV_RANGE_MIN] << 4);
 }
 
-static inline void VP8YuvToArgb4444(uint8_t y, uint8_t u, uint8_t v,
+static inline void VP8YuvToRgba4444(uint8_t y, uint8_t u, uint8_t v,
                                     uint8_t* const argb) {
-  argb[0] = 0xf0;
-  VP8YuvToArgb4444KeepA(y, u, v, argb);
+  argb[1] = 0x0f;
+  VP8YuvToRgba4444KeepA(y, u, v, argb);
 }
 
 static inline void VP8YuvToBgr(uint8_t y, uint8_t u, uint8_t v,

src/webp/decode.h

@@ -67,7 +67,7 @@ WEBP_EXTERN(uint8_t*) WebPDecodeYUV(const uint8_t* data, uint32_t data_size,
                                     uint8_t** u, uint8_t** v,
                                     int* stride, int* uv_stride);
 
-// These three functions are variants of the above ones, that decode the image
+// These five functions are variants of the above ones, that decode the image
 // directly into a pre-allocated buffer 'output_buffer'. The maximum storage
 // available in this buffer is indicated by 'output_buffer_size'. If this
 // storage is not sufficient (or an error occurred), NULL is returned.
@@ -81,6 +81,9 @@ WEBP_EXTERN(uint8_t*) WebPDecodeRGBInto(
 WEBP_EXTERN(uint8_t*) WebPDecodeRGBAInto(
     const uint8_t* data, uint32_t data_size,
     uint8_t* output_buffer, int output_buffer_size, int output_stride);
+WEBP_EXTERN(uint8_t*) WebPDecodeARGBInto(
+    const uint8_t* data, uint32_t data_size,
+    uint8_t* output_buffer, int output_buffer_size, int output_stride);
 // BGR variants
 WEBP_EXTERN(uint8_t*) WebPDecodeBGRInto(
     const uint8_t* data, uint32_t data_size,
@@ -108,7 +111,7 @@ WEBP_EXTERN(uint8_t*) WebPDecodeYUVInto(
 // Colorspaces
 typedef enum { MODE_RGB = 0, MODE_RGBA = 1,
                MODE_BGR = 2, MODE_BGRA = 3,
-               MODE_ARGB = 4, MODE_ARGB_4444 = 5,
+               MODE_ARGB = 4, MODE_RGBA_4444 = 5,
                MODE_RGB_565 = 6,
                // YUV modes must come after RGB ones.
                MODE_YUV = 7, MODE_YUVA = 8,  // yuv 4:2:0