ok, add a8 dst support

Change-Id: Ib7f855c833c8e73f448de7c8a75f59b1a0880874
Reviewed-on: https://skia-review.googlesource.com/53600
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>

2 files changed, 32 insertions, 2 deletions

diff --git a/tools/ok_dsts.cpp b/tools/ok_dsts.cpp
index c25a8d5fee..1f4fe42a4b 100644
--- a/tools/ok_dsts.cpp
+++ b/tools/ok_dsts.cpp
@@ -14,6 +14,7 @@ struct SWDst : Dst {
 
     static std::unique_ptr<Dst> Create(Options options) {
         SkImageInfo info = SkImageInfo::MakeN32Premul(0,0);
+        if (options("ct") == "a8")  { info = info.makeColorType(kAlpha_8_SkColorType); }
         if (options("ct") == "565") { info = info.makeColorType(kRGB_565_SkColorType); }
         if (options("ct") == "f16") { info = info.makeColorType(kRGBA_F16_SkColorType); }
 
@@ -41,6 +42,11 @@ struct SWDst : Dst {
 static Register sw{"sw", "draw with the software backend", SWDst::Create};
 static Register _8888{"8888", "alias for sw", SWDst::Create};
 
+static Register a8{"a8", "alias for sw:ct=a8", [](Options options) {
+    options["ct"] = "a8";
+    return SWDst::Create(options);
+}};
+
 static Register _565{"565", "alias for sw:ct=565", [](Options options) {
     options["ct"] = "565";
     return SWDst::Create(options);
diff --git a/tools/ok_vias.cpp b/tools/ok_vias.cpp
index a2f4492d4f..815b159a01 100644
--- a/tools/ok_vias.cpp
+++ b/tools/ok_vias.cpp
@@ -6,6 +6,7 @@
  */
 
 #include "ProcStats.h"
+#include "SkColorFilter.h"
 #include "SkEventTracingPriv.h"
 #include "SkImage.h"
 #include "SkOSFile.h"
@@ -135,9 +136,32 @@ struct Png : Dst {
         }
 
         SkBitmap bm;
+        if (!target->image()->asLegacyBitmap(&bm, SkImage::kRO_LegacyBitmapMode)) {
+            return Status::Failed;
+        }
+
+        // SkPngEncoder can't encode A8 .pngs, and even if it could, they'd be a pain to look at.
+        if (bm.colorType() == kAlpha_8_SkColorType) {
+            SkPaint paint;
+            SkScalar alpha_to_opaque_gray[20] = {
+                0,0,0,1,  0,  // red   = alpha
+                0,0,0,1,  0,  // green = alpha
+                0,0,0,1,  0,  // blue  = alpha
+                0,0,0,0,255,  // alpha = 255
+            };
+            paint.setColorFilter(SkColorFilter::MakeMatrixFilterRowMajor255(alpha_to_opaque_gray));
+            paint.setBlendMode(SkBlendMode::kSrc);
+
+            SkBitmap dst;
+            dst.allocN32Pixels(bm.width(), bm.height(), /*isOpaque=*/true);
+            SkCanvas canvas(dst);
+            canvas.drawBitmap(bm, 0,0, &paint);
+
+            bm = dst;
+        }
+
         SkPixmap pm;
-        if (!target->image()->asLegacyBitmap(&bm, SkImage::kRO_LegacyBitmapMode) ||
-            !bm.peekPixels(&pm)) {
+        if (!bm.peekPixels(&pm)) {
             return Status::Failed;
         }