SurfaceTexture: shrink all sides when cropping

This change makes SurfaceTexture include an offset for all sides of the crop
region when cropping.  This keeps the image centered, to minimize the visual
changes when switching between the texture transform matrix-based cropping and
something that does proper cropping (e.g. HWComposer).

Change-Id: I541d3046fd92e49221b488444df36d490924d1c5

diff --git a/libs/gui/SurfaceTexture.cpp b/libs/gui/SurfaceTexture.cpp
index 0fa9ca1..ed1ea4e 100644 (file)
--- a/libs/gui/SurfaceTexture.cpp
+++ b/libs/gui/SurfaceTexture.cpp
@@ -542,28 +542,16 @@ void SurfaceTexture::computeCurrentTransformMatrix() {
         // decoder, camera, etc.) would simply not use a crop rectangle (or at
         // least not tell the framework about it) so that the GPU can do the
         // correct edge behavior.
-        int xshrink = 0, yshrink = 0;
-        if (mCurrentCrop.left > 0) {
-            tx = float(mCurrentCrop.left + 1) / float(buf->getWidth());
-            xshrink++;
-        } else {
-            tx = 0.0f;
-        }
-        if (mCurrentCrop.right < int32_t(buf->getWidth())) {
-            xshrink++;
-        }
-        if (mCurrentCrop.bottom < int32_t(buf->getHeight())) {
-            ty = (float(buf->getHeight() - mCurrentCrop.bottom) + 1.0f) /
-                    float(buf->getHeight());
-            yshrink++;
-        } else {
-            ty = 0.0f;
-        }
-        if (mCurrentCrop.top > 0) {
-            yshrink++;
-        }
-        sx = float(mCurrentCrop.width() - xshrink) / float(buf->getWidth());
-        sy = float(mCurrentCrop.height() - yshrink) / float(buf->getHeight());
+        const float shrinkAmount = 1.0f; // the amount that each edge is shrunk
+
+        tx = (float(mCurrentCrop.left) + shrinkAmount) /
+                float(buf->getWidth());
+        ty = (float(buf->getHeight() - mCurrentCrop.bottom) +
+                shrinkAmount) / float(buf->getHeight());
+        sx = (float(mCurrentCrop.width()) - (2.0f * shrinkAmount)) /
+                float(buf->getWidth());
+        sy = (float(mCurrentCrop.height()) - (2.0f * shrinkAmount)) /
+                float(buf->getHeight());
     } else {
         tx = 0.0f;
         ty = 0.0f;

diff --git a/libs/gui/tests/SurfaceTextureClient_test.cpp b/libs/gui/tests/SurfaceTextureClient_test.cpp
index aa1f94e..b576ca5 100644 (file)
--- a/libs/gui/tests/SurfaceTextureClient_test.cpp
+++ b/libs/gui/tests/SurfaceTextureClient_test.cpp
@@ -580,13 +580,13 @@ TEST_F(SurfaceTextureClientTest, GetTransformMatrixSucceedsAfterFreeingBuffersWi
 
     // This accounts for the 1 texel shrink for each edge that's included in the
     // transform matrix to avoid texturing outside the crop region.
-    EXPECT_EQ(.5f, mtx[0]);
+    EXPECT_EQ(.375f, mtx[0]);
     EXPECT_EQ(0.f, mtx[1]);
     EXPECT_EQ(0.f, mtx[2]);
     EXPECT_EQ(0.f, mtx[3]);
 
     EXPECT_EQ(0.f, mtx[4]);
-    EXPECT_EQ(-.5f, mtx[5]);
+    EXPECT_EQ(-.375f, mtx[5]);
     EXPECT_EQ(0.f, mtx[6]);
     EXPECT_EQ(0.f, mtx[7]);
 
@@ -595,7 +595,7 @@ TEST_F(SurfaceTextureClientTest, GetTransformMatrixSucceedsAfterFreeingBuffersWi
     EXPECT_EQ(1.f, mtx[10]);
     EXPECT_EQ(0.f, mtx[11]);
 
-    EXPECT_EQ(0.f, mtx[12]);
+    EXPECT_EQ(.125f, mtx[12]);
     EXPECT_EQ(.5f, mtx[13]);
     EXPECT_EQ(0.f, mtx[14]);
     EXPECT_EQ(1.f, mtx[15]);