Properly convert A8 -> RGBA_8888 gainmap contents

When doing the fallback from alpha8 to rgba8888 when
alpha8 gralloc buffers are not available, we need to convert
the contents as well to ensure that the gainmap shader
processes the correct channel(s)

Bug: 356778382
Test: silkfx w/ hardware allocation; updated uirendering GainmapTests
Flag: EXEMPT bugfix
Change-Id: I4bc571cd9e1f7715a1e269e516ce2678df297274

1 files changed, 26 insertions, 1 deletions

diff --git a/libs/hwui/Gainmap.cpp b/libs/hwui/Gainmap.cpp
index 30f401ef5f01..ea955e25dc2f 100644
--- a/libs/hwui/Gainmap.cpp
+++ b/libs/hwui/Gainmap.cpp
@@ -15,12 +15,37 @@
  */
 #include "Gainmap.h"
 
+#include <SkBitmap.h>
+#include <SkCanvas.h>
+#include <SkColorFilter.h>
+#include <SkImagePriv.h>
+#include <SkPaint.h>
+
+#include "HardwareBitmapUploader.h"
+
 namespace android::uirenderer {
 
 sp<Gainmap> Gainmap::allocateHardwareGainmap(const sp<Gainmap>& srcGainmap) {
     auto gainmap = sp<Gainmap>::make();
     gainmap->info = srcGainmap->info;
-    const SkBitmap skSrcBitmap = srcGainmap->bitmap->getSkBitmap();
+    SkBitmap skSrcBitmap = srcGainmap->bitmap->getSkBitmap();
+    if (skSrcBitmap.info().colorType() == kAlpha_8_SkColorType &&
+        !HardwareBitmapUploader::hasAlpha8Support()) {
+        // The regular Bitmap::allocateHardwareBitmap will do a conversion that preserves channels,
+        // so alpha8 maps to the alpha channel of rgba. However, for gainmaps we will interpret
+        // the data of an rgba buffer differently as we'll only look at the rgb channels
+        // So we need to map alpha8 to rgbx_8888 essentially
+        SkBitmap bitmap;
+        bitmap.allocPixels(skSrcBitmap.info().makeColorType(kN32_SkColorType));
+        SkCanvas canvas(bitmap);
+        SkPaint paint;
+        const float alphaToOpaque[] = {0, 0, 0, 1, 0, 0, 0, 0, 1, 0,
+                                       0, 0, 0, 1, 0, 0, 0, 0, 0, 255};
+        paint.setColorFilter(SkColorFilters::Matrix(alphaToOpaque, SkColorFilters::Clamp::kNo));
+        canvas.drawImage(SkMakeImageFromRasterBitmap(skSrcBitmap, kNever_SkCopyPixelsMode), 0, 0,
+                         SkSamplingOptions{}, &paint);
+        skSrcBitmap = bitmap;
+    }
     sk_sp<Bitmap> skBitmap(Bitmap::allocateHardwareBitmap(skSrcBitmap));
     if (!skBitmap.get()) {
         return nullptr;