speedup mipmap building

src/core/SkMipMap.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkMipMap.h"
 #include "SkBitmap.h"
 #include "SkColorPriv.h"
 
-static void downsampleby2_proc32(SkBitmap* dst, int x, int y,
-                                 const SkBitmap& src) {
+static void downsample32_nocheck(void* dst, int, int, const void* srcPtr, const SkBitmap& srcBM) {
+    const uint32_t* p = static_cast<const uint32_t*>(srcPtr);
+    const uint32_t* baseP = p;
+    uint32_t c, ag, rb;
+
+    c = *p; ag = (c >> 8) & 0xFF00FF; rb = c & 0xFF00FF;
+    p += 1;
+
+    c = *p; ag += (c >> 8) & 0xFF00FF; rb += c & 0xFF00FF;
+
+    p = baseP;
+    p += srcBM.rowBytes() >> 2;
+
+    c = *p; ag += (c >> 8) & 0xFF00FF; rb += c & 0xFF00FF;
+    p += 1;
+
+    c = *p; ag += (c >> 8) & 0xFF00FF; rb += c & 0xFF00FF;
+
+    *(uint32_t*)dst = ((rb >> 2) & 0xFF00FF) | ((ag << 6) & 0xFF00FF00);
+}
+
+static void downsample32_check(void* dst, int x, int y, const void* srcPtr, const SkBitmap& srcBM) {
+    const uint32_t* p = static_cast<const uint32_t*>(srcPtr);
+    const uint32_t* baseP = p;
+
     x <<= 1;
     y <<= 1;
-    const SkPMColor* p = src.getAddr32(x, y);
-    const SkPMColor* baseP = p;
+    SkASSERT(srcBM.getAddr32(x, y) == p);
+
     SkPMColor c, ag, rb;
 
     c = *p; ag = (c >> 8) & 0xFF00FF; rb = c & 0xFF00FF;
-    if (x < src.width() - 1) {
+    if (x < srcBM.width() - 1) {
         p += 1;
     }
     c = *p; ag += (c >> 8) & 0xFF00FF; rb += c & 0xFF00FF;
 
     p = baseP;
-    if (y < src.height() - 1) {
-        p += src.rowBytes() >> 2;
+    if (y < srcBM.height() - 1) {
+        p += srcBM.rowBytes() >> 2;
     }
     c = *p; ag += (c >> 8) & 0xFF00FF; rb += c & 0xFF00FF;
-    if (x < src.width() - 1) {
+    if (x < srcBM.width() - 1) {
         p += 1;
     }
     c = *p; ag += (c >> 8) & 0xFF00FF; rb += c & 0xFF00FF;
 
-    *dst->getAddr32(x >> 1, y >> 1) =
-    ((rb >> 2) & 0xFF00FF) | ((ag << 6) & 0xFF00FF00);
+    *((uint32_t*)dst) = ((rb >> 2) & 0xFF00FF) | ((ag << 6) & 0xFF00FF00);
 }
 
 static inline uint32_t expand16(U16CPU c) {
     return (c & ~SK_G16_MASK_IN_PLACE) | ((c & SK_G16_MASK_IN_PLACE) << 16);
 }
 
 // returns dirt in the top 16bits, but we don't care, since we only
 // store the low 16bits.
 static inline U16CPU pack16(uint32_t c) {
     return (c & ~SK_G16_MASK_IN_PLACE) | ((c >> 16) & SK_G16_MASK_IN_PLACE);
 }
 
-static void downsampleby2_proc16(SkBitmap* dst, int x, int y,
-                                 const SkBitmap& src) {
+static void downsample16(void* dst, int x, int y, const void* srcPtr, const SkBitmap& srcBM) {
+    const uint16_t* p = static_cast<const uint16_t*>(srcPtr);
+    const uint16_t* baseP = p;
+
     x <<= 1;
     y <<= 1;
-    const uint16_t* p = src.getAddr16(x, y);
-    const uint16_t* baseP = p;
-    SkPMColor       c;
+    SkASSERT(srcBM.getAddr16(x, y) == p);
+
+    SkPMColor c;
 
     c = expand16(*p);
-    if (x < src.width() - 1) {
+    if (x < srcBM.width() - 1) {
         p += 1;
     }
     c += expand16(*p);
 
     p = baseP;
-    if (y < src.height() - 1) {
-        p += src.rowBytes() >> 1;
+    if (y < srcBM.height() - 1) {
+        p += srcBM.rowBytes() >> 1;
     }
     c += expand16(*p);
-    if (x < src.width() - 1) {
+    if (x < srcBM.width() - 1) {
         p += 1;
     }
     c += expand16(*p);
 
-    *dst->getAddr16(x >> 1, y >> 1) = (uint16_t)pack16(c >> 2);
+    *((uint16_t*)dst) = (uint16_t)pack16(c >> 2);
 }
 
 static uint32_t expand4444(U16CPU c) {
     return (c & 0xF0F) | ((c & ~0xF0F) << 12);
 }
 
 static U16CPU collaps4444(uint32_t c) {
     return (c & 0xF0F) | ((c >> 12) & ~0xF0F);
 }
 
-static void downsampleby2_proc4444(SkBitmap* dst, int x, int y,
-                                   const SkBitmap& src) {
+static void downsample4444(void* dst, int x, int y, const void* srcPtr, const SkBitmap& srcBM) {
+    const uint16_t* p = static_cast<const uint16_t*>(srcPtr);
+    const uint16_t* baseP = p;
+
     x <<= 1;
     y <<= 1;
-    const uint16_t* p = src.getAddr16(x, y);
-    const uint16_t* baseP = p;
-    uint32_t        c;
+    SkASSERT(srcBM.getAddr16(x, y) == p);
+
+    uint32_t c;
 
     c = expand4444(*p);
-    if (x < src.width() - 1) {
+    if (x < srcBM.width() - 1) {
         p += 1;
     }
     c += expand4444(*p);
 
     p = baseP;
-    if (y < src.height() - 1) {
-        p += src.rowBytes() >> 1;
+    if (y < srcBM.height() - 1) {
+        p += srcBM.rowBytes() >> 1;
     }
     c += expand4444(*p);
-    if (x < src.width() - 1) {
+    if (x < srcBM.width() - 1) {
         p += 1;
     }
     c += expand4444(*p);
 
-    *dst->getAddr16(x >> 1, y >> 1) = (uint16_t)collaps4444(c >> 2);
+   *((uint16_t*)dst) = (uint16_t)collaps4444(c >> 2);
 }
 
 size_t SkMipMap::AllocLevelsSize(int levelCount, size_t pixelSize) {
     if (levelCount < 0) {
         return 0;
     }
     int64_t size = sk_64_mul(levelCount + 1, sizeof(Level)) + pixelSize;
     if (!sk_64_isS32(size)) {
         return 0;
     }
     return sk_64_asS32(size);
 }
 
+typedef void SkDownSampleProc(void*, int x, int y, const void* srcPtr, const SkBitmap& srcBM);
+
 SkMipMap* SkMipMap::Build(const SkBitmap& src, SkDiscardableFactoryProc fact) {
-    void (*proc)(SkBitmap* dst, int x, int y, const SkBitmap& src);
+    SkDownSampleProc* proc_nocheck, *proc_check;
 
     const SkColorType ct = src.colorType();
     const SkAlphaType at = src.alphaType();
     switch (ct) {
         case kRGBA_8888_SkColorType:
         case kBGRA_8888_SkColorType:
-            proc = downsampleby2_proc32;
+            proc_check = downsample32_check;
+            proc_nocheck = downsample32_nocheck;
             break;
         case kRGB_565_SkColorType:
-            proc = downsampleby2_proc16;
+            proc_check = downsample16;
+            proc_nocheck = proc_check;
             break;
         case kARGB_4444_SkColorType:
-            proc = downsampleby2_proc4444;
+            proc_check = downsample4444;
+            proc_nocheck = proc_check;
             break;
         default:
             return NULL; // don't build mipmaps for any other colortypes (yet)
     }
 
     SkAutoLockPixels alp(src);
     if (!src.readyToDraw()) {
         return NULL;
     }
 
@@ skipping 53 matching lines @@
         levels[i].fPixels   = addr;
         levels[i].fWidth    = width;
         levels[i].fHeight   = height;
         levels[i].fRowBytes = rowBytes;
         levels[i].fScale    = (float)width / src.width();
 
         SkBitmap dstBM;
         dstBM.installPixels(SkImageInfo::Make(width, height, ct, at), addr, rowBytes);
 
         srcBM.lockPixels();
-        for (int y = 0; y < height; y++) {
+        const int widthEven = width & ~1;
+        const int heightEven = height & ~1;
+        const size_t pixelSize = srcBM.info().bytesPerPixel();
+
+        const void* srcBasePtr = srcBM.getPixels();
+        void* dstBasePtr = dstBM.getPixels();
+        for (int y = 0; y < heightEven; y++) {
+            const void* srcPtr = srcBasePtr;
+            void* dstPtr = dstBasePtr;
+            for (int x = 0; x < widthEven; x++) {
+                proc_nocheck(dstPtr, x, y, srcPtr, srcBM);
+                srcPtr = (char*)srcPtr + pixelSize * 2;
+                dstPtr = (char*)dstPtr + pixelSize;
+            }
+            if (width & 1) {
+                proc_check(dstPtr, widthEven, y, srcPtr, srcBM);
+            }
+
+            srcBasePtr = (char*)srcBasePtr + srcBM.rowBytes() * 2;
+            dstBasePtr = (char*)dstBasePtr + dstBM.rowBytes();
+        }
+        if (height & 1) {
+            const void* srcPtr = srcBasePtr;
+            void* dstPtr = dstBasePtr;
             for (int x = 0; x < width; x++) {
-                proc(&dstBM, x, y, srcBM);
+                proc_check(dstPtr, x, heightEven, srcPtr, srcBM);
+                srcPtr = (char*)srcPtr + pixelSize * 2;
+                dstPtr = (char*)dstPtr + pixelSize;
             }
         }
+
         srcBM.unlockPixels();
 
         srcBM = dstBM;
         addr += height * rowBytes;
     }
     SkASSERT(addr == baseAddr + size);
 
     return mipmap;
 }
 
@@ skipping 22 matching lines @@
     }
 
     if (level > fCount) {
         level = fCount;
     }
     if (levelPtr) {
         *levelPtr = fLevels[level - 1];
     }
     return true;
 }