libwebp: update to 0.4.1

third_party/libwebp/dsp/alpha_processing.c

Index: third_party/libwebp/dsp/alpha_processing.c
diff --git a/third_party/libwebp/utils/alpha_processing.c b/third_party/libwebp/dsp/alpha_processing.c
similarity index 72%
rename from third_party/libwebp/utils/alpha_processing.c
rename to third_party/libwebp/dsp/alpha_processing.c
index 7362ff94a54f3593c8ed67a0b635d0a070b9c81e..09deacfb9332869a0d4acc1489b8bc4624f0380d 100644
--- a/third_party/libwebp/utils/alpha_processing.c
+++ b/third_party/libwebp/dsp/alpha_processing.c
@@ -12,7 +12,7 @@
 // Author: Skal (pascal.massimino@gmail.com)
 
 #include <assert.h>
-#include "./alpha_processing.h"
+#include "./dsp.h"
 
 // Tables can be faster on some platform but incur some extra binary size (~2k).
 // #define USE_TABLES_FOR_ALPHA_MULT
@@ -134,7 +134,7 @@ static WEBP_INLINE uint32_t GetScale(uint32_t a, int inverse) {
 
 #endif    // USE_TABLES_FOR_ALPHA_MULT
 
-void WebPMultARGBRow(uint32_t* const ptr, int width, int inverse) {
+static void MultARGBRow(uint32_t* const ptr, int width, int inverse) {
   int x;
   for (x = 0; x < width; ++x) {
     const uint32_t argb = ptr[x];
@@ -154,17 +154,8 @@ void WebPMultARGBRow(uint32_t* const ptr, int width, int inverse) {
   }
 }
 
-void WebPMultARGBRows(uint8_t* ptr, int stride, int width, int num_rows,
-                      int inverse) {
-  int n;
-  for (n = 0; n < num_rows; ++n) {
-    WebPMultARGBRow((uint32_t*)ptr, width, inverse);
-    ptr += stride;
-  }
-}
-
-void WebPMultRow(uint8_t* const ptr, const uint8_t* const alpha,
-                 int width, int inverse) {
+static void MultRow(uint8_t* const ptr, const uint8_t* const alpha,
+                    int width, int inverse) {
   int x;
   for (x = 0; x < width; ++x) {
     const uint32_t a = alpha[x];
@@ -179,6 +170,26 @@ void WebPMultRow(uint8_t* const ptr, const uint8_t* const alpha,
   }
 }
 
+#undef KINV_255
+#undef HALF
+#undef MFIX
+
+void (*WebPMultARGBRow)(uint32_t* const ptr, int width, int inverse);
+void (*WebPMultRow)(uint8_t* const ptr, const uint8_t* const alpha,
+                    int width, int inverse);
+
+//------------------------------------------------------------------------------
+// Generic per-plane calls
+
+void WebPMultARGBRows(uint8_t* ptr, int stride, int width, int num_rows,
+                      int inverse) {
+  int n;
+  for (n = 0; n < num_rows; ++n) {
+    WebPMultARGBRow((uint32_t*)ptr, width, inverse);
+    ptr += stride;
+  }
+}
+
 void WebPMultRows(uint8_t* ptr, int stride,
                   const uint8_t* alpha, int alpha_stride,
                   int width, int num_rows, int inverse) {
@@ -190,7 +201,98 @@ void WebPMultRows(uint8_t* ptr, int stride,
   }
 }
 
-#undef KINV_255
-#undef HALF
-#undef MFIX
+//------------------------------------------------------------------------------
+// Premultiplied modes
+
+// non dithered-modes
+
+// (x * a * 32897) >> 23 is bit-wise equivalent to (int)(x * a / 255.)
+// for all 8bit x or a. For bit-wise equivalence to (int)(x * a / 255. + .5),
+// one can use instead: (x * a * 65793 + (1 << 23)) >> 24
+#if 1     // (int)(x * a / 255.)
+#define MULTIPLIER(a)   ((a) * 32897U)
+#define PREMULTIPLY(x, m) (((x) * (m)) >> 23)
+#else     // (int)(x * a / 255. + .5)
+#define MULTIPLIER(a) ((a) * 65793U)
+#define PREMULTIPLY(x, m) (((x) * (m) + (1U << 23)) >> 24)
+#endif
+
+static void ApplyAlphaMultiply(uint8_t* rgba, int alpha_first,
+                               int w, int h, int stride) {
+  while (h-- > 0) {
+    uint8_t* const rgb = rgba + (alpha_first ? 1 : 0);
+    const uint8_t* const alpha = rgba + (alpha_first ? 0 : 3);
+    int i;
+    for (i = 0; i < w; ++i) {
+      const uint32_t a = alpha[4 * i];
+      if (a != 0xff) {
+        const uint32_t mult = MULTIPLIER(a);
+        rgb[4 * i + 0] = PREMULTIPLY(rgb[4 * i + 0], mult);
+        rgb[4 * i + 1] = PREMULTIPLY(rgb[4 * i + 1], mult);
+        rgb[4 * i + 2] = PREMULTIPLY(rgb[4 * i + 2], mult);
+      }
+    }
+    rgba += stride;
+  }
+}
+#undef MULTIPLIER
+#undef PREMULTIPLY
+
+// rgbA4444
+
+#define MULTIPLIER(a)  ((a) * 0x1111)    // 0x1111 ~= (1 << 16) / 15
+
+static WEBP_INLINE uint8_t dither_hi(uint8_t x) {
+  return (x & 0xf0) | (x >> 4);
+}
+
+static WEBP_INLINE uint8_t dither_lo(uint8_t x) {
+  return (x & 0x0f) | (x << 4);
+}
+
+static WEBP_INLINE uint8_t multiply(uint8_t x, uint32_t m) {
+  return (x * m) >> 16;
+}
+
+static WEBP_INLINE void ApplyAlphaMultiply4444(uint8_t* rgba4444,
+                                               int w, int h, int stride,
+                                               int rg_byte_pos /* 0 or 1 */) {
+  while (h-- > 0) {
+    int i;
+    for (i = 0; i < w; ++i) {
+      const uint32_t rg = rgba4444[2 * i + rg_byte_pos];
+      const uint32_t ba = rgba4444[2 * i + (rg_byte_pos ^ 1)];
+      const uint8_t a = ba & 0x0f;
+      const uint32_t mult = MULTIPLIER(a);
+      const uint8_t r = multiply(dither_hi(rg), mult);
+      const uint8_t g = multiply(dither_lo(rg), mult);
+      const uint8_t b = multiply(dither_hi(ba), mult);
+      rgba4444[2 * i + rg_byte_pos] = (r & 0xf0) | ((g >> 4) & 0x0f);
+      rgba4444[2 * i + (rg_byte_pos ^ 1)] = (b & 0xf0) | a;
+    }
+    rgba4444 += stride;
+  }
+}
+#undef MULTIPLIER
 
+static void ApplyAlphaMultiply_16b(uint8_t* rgba4444,
+                                   int w, int h, int stride) {
+#ifdef WEBP_SWAP_16BIT_CSP
+  ApplyAlphaMultiply4444(rgba4444, w, h, stride, 1);
+#else
+  ApplyAlphaMultiply4444(rgba4444, w, h, stride, 0);
+#endif
+}
+
+void (*WebPApplyAlphaMultiply)(uint8_t*, int, int, int, int);
+void (*WebPApplyAlphaMultiply4444)(uint8_t*, int, int, int);
+
+//------------------------------------------------------------------------------
+// Init function
+
+void WebPInitAlphaProcessing(void) {
+  WebPMultARGBRow = MultARGBRow;
+  WebPMultRow = MultRow;
+  WebPApplyAlphaMultiply = ApplyAlphaMultiply;
+  WebPApplyAlphaMultiply4444 = ApplyAlphaMultiply_16b;
+}