encode kAlpha_8 as grayalpha with sigbits for gray==1

Bug: skia:
Change-Id: Ib61e8e0f62af92d8746f5e73469002e7804a8447
Reviewed-on: https://skia-review.googlesource.com/78481
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Mike Reed <reed@google.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/codec/SkCodec.cpp b/src/codec/SkCodec.cpp
index 59978c6fdf..a0f1fb2706 100644
--- a/src/codec/SkCodec.cpp
+++ b/src/codec/SkCodec.cpp
@@ -175,6 +175,10 @@ bool SkCodec::conversionSupported(const SkImageInfo& dst, SkEncodedInfo::Color s
         case kGray_8_SkColorType:
             return SkEncodedInfo::kGray_Color == srcColor && srcIsOpaque &&
                    !needs_color_xform(dst, srcCS, false);
+        case kAlpha_8_SkColorType:
+            // conceptually we can convert anything into alpha_8, but we haven't actually coded
+            // all of those other conversions yet, so only return true for the case we have codec.
+            return fSrcInfo.colorType() == kAlpha_8_SkColorType;;
         default:
             return false;
     }