Support more swizzles to 565 in SkCodec

src/codec/SkCodecPriv.h

Index: src/codec/SkCodecPriv.h
diff --git a/src/codec/SkCodecPriv.h b/src/codec/SkCodecPriv.h
index 2596787b9b7aadcf44819e23849467b137c48cc7..450457f630137c98b854be9f2ad8ad963f8c71d0 100644
--- a/src/codec/SkCodecPriv.h
+++ b/src/codec/SkCodecPriv.h
@@ -53,6 +53,35 @@ static inline bool valid_alpha(SkAlphaType dstAlpha, SkAlphaType srcAlpha) {
 }
 
 /*
+ * Most of our codecs support the same conversions:
+ * - profileType must be the same
+ * - opaque only to opaque (and 565 only if opaque)
+ * - premul to unpremul and vice versa
+ * - always support N32
+ * - otherwise match the src color type
+ */
+static bool conversion_possible(const SkImageInfo& dst, const SkImageInfo& src) {

[scroggo_chromium, 2015/08/10 17:26:16]

This function is a simplified version of the method that showed up in other
files.

[msarett, 2015/08/10 17:44:24]

Nice!  This is a big improvement.

+    if (dst.profileType() != src.profileType()) {
+        return false;
+    }
+
+    // Ensure the alpha type is valid
+    if (!valid_alpha(dst.alphaType(), src.alphaType())) {
+        return false;
+    }
+
+    // Check for supported color types
+    switch (dst.colorType()) {
+        case kN32_SkColorType:
+            return true;
+        case kRGB_565_SkColorType:

[scroggo_chromium, 2015/08/10 17:26:16]

This part is different - I've added support for 565, if the source is opaque.

+            return src.alphaType() == kOpaque_SkAlphaType;
+        default:
+            return dst.colorType() == src.colorType();

[scroggo_chromium, 2015/08/10 17:26:16]

Some versions of conversion_possible checked specifically for index8. That is
covered by this check.

+    }
+}
+
+/*
  * If there is a color table, get a pointer to the colors, otherwise return NULL
  */
 static const SkPMColor* get_color_ptr(SkColorTable* colorTable) {