Add SkCanvas::writePixels that takes info+pixels directly

tools/sk_tool_utils.cpp

+#include "sk_tool_utils.h"
+
+namespace sk_tool_utils {
+
+void config8888_to_imagetypes(SkCanvas::Config8888 config, SkColorType* ct, SkAlphaType* at) {
+    switch (config) {
+        case SkCanvas::kNative_Premul_Config8888:
+            *ct = kPMColor_SkColorType;
+            *at = kPremul_SkAlphaType;
+            break;
+        case SkCanvas::kNative_Unpremul_Config8888:
+            *ct = kPMColor_SkColorType;
+            *at = kUnpremul_SkAlphaType;
+            break;
+        case SkCanvas::kBGRA_Premul_Config8888:
+            *ct = kBGRA_8888_SkColorType;
+            *at = kPremul_SkAlphaType;
+            break;
+        case SkCanvas::kBGRA_Unpremul_Config8888:
+            *ct = kBGRA_8888_SkColorType;
+            *at = kUnpremul_SkAlphaType;
+            break;
+        case SkCanvas::kRGBA_Premul_Config8888:
+            *ct = kRGBA_8888_SkColorType;
+            *at = kPremul_SkAlphaType;
+            break;
+        case SkCanvas::kRGBA_Unpremul_Config8888:
+            *ct = kRGBA_8888_SkColorType;
+            *at = kUnpremul_SkAlphaType;
+            break;
+        default:
+            SkASSERT(0);
+    }
+}
+
+void write_pixels(SkCanvas* canvas, const SkBitmap& bitmap, int x, int y,
+                  SkColorType colorType, SkAlphaType alphaType) {
+    SkBitmap tmp(bitmap);
+    tmp.lockPixels();
+    
+    SkImageInfo info = tmp.info();
+    info.fColorType = colorType;
+    info.fAlphaType = alphaType;
+    
+    canvas->writePixels(info, tmp.getPixels(), tmp.rowBytes(), x, y);
+}
+
+}