add kGray_8_SkColorType

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"
@@ skipping 117 matching lines @@
     }
     c += expand4444(*p);
     if (x < srcBM.width() - 1) {
         p += 1;
     }
     c += expand4444(*p);
 
    *((uint16_t*)dst) = (uint16_t)collaps4444(c >> 2);
 }
 
+static void downsample8_nocheck(void* dst, int, int, const void* srcPtr, const SkBitmap& srcBM) {
+    const size_t rb = srcBM.rowBytes();
+    const uint8_t* p = static_cast<const uint8_t*>(srcPtr);
+    *(uint8_t*)dst = (p[0] + p[1] + p[rb] + p[rb + 1]) >> 2;
+}
+
+static void downsample8_check(void* dst, int x, int y, const void* srcPtr, const SkBitmap& srcBM) {
+    const uint8_t* p = static_cast<const uint8_t*>(srcPtr);
+    const uint8_t* baseP = p;
+
+    x <<= 1;
+    y <<= 1;
+    SkASSERT(srcBM.getAddr8(x, y) == p);
+
+    unsigned c = *p;
+    if (x < srcBM.width() - 1) {
+        p += 1;
+    }
+    c += *p;
+
+    p = baseP;
+    if (y < srcBM.height() - 1) {
+        p += srcBM.rowBytes();
+    }
+    c += *p;
+    if (x < srcBM.width() - 1) {
+        p += 1;
+    }
+    c += *p;
+
+    *(uint8_t*)dst = 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);
 }
@@ skipping 12 matching lines @@
             proc_nocheck = downsample32_nocheck;
             break;
         case kRGB_565_SkColorType:
             proc_check = downsample16;
             proc_nocheck = proc_check;
             break;
         case kARGB_4444_SkColorType:
             proc_check = downsample4444;
             proc_nocheck = proc_check;
             break;
+        case kAlpha_8_SkColorType:
+        case kGray_8_SkColorType:
+            proc_check = downsample8_check;
+            proc_nocheck = downsample8_nocheck;
+            break;
         default:
             return NULL; // don't build mipmaps for any other colortypes (yet)
     }
 
     SkAutoLockPixels alp(src);
     if (!src.readyToDraw()) {
         return NULL;
     }
 
     // whip through our loop to compute the exact size needed
@@ skipping 125 matching lines @@
     }
 
     if (level > fCount) {
         level = fCount;
     }
     if (levelPtr) {
         *levelPtr = fLevels[level - 1];
     }
     return true;
 }