Do not use GrBicubic effect when downscaling. Also, don't use glTexStorage as it interferes with de…

src/core/SkBitmapProcShader.cpp

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkColorPriv.h"
 #include "SkFlattenableBuffers.h"
 #include "SkPixelRef.h"
@@ skipping 339 matching lines @@
 
 #if SK_SUPPORT_GPU
 
 #include "GrTextureAccess.h"
 #include "effects/GrSimpleTextureEffect.h"
 #include "SkGr.h"
 
 GrEffectRef* SkBitmapProcShader::asNewEffect(GrContext* context, const SkPaint& paint) const {
     SkMatrix matrix;
     matrix.setIDiv(fRawBitmap.width(), fRawBitmap.height());
 

[robertphillips, 2013/12/04 23:31:55]

Why remove this stuff?

[bsalomon, 2013/12/09 18:44:31]

It's from when SkShader lazily allocated and stored a matrix rather than just
always having a matrix and init'ing it to I. Both invert and perConcat have fast
paths for I.

-    if (this->hasLocalMatrix()) {
-        SkMatrix inverse;
-        if (!this->getLocalMatrix().invert(&inverse)) {
-            return NULL;
-        }
-        matrix.preConcat(inverse);
+    SkMatrix inverse;
+    if (!this->getLocalMatrix().invert(&inverse)) {
+        return NULL;
     }
+    matrix.preConcat(inverse);
+
     SkShader::TileMode tm[] = {
         (TileMode)fState.fTileModeX,
         (TileMode)fState.fTileModeY,
     };
 
     // Must set wrap and filter on the sampler before requesting a texture.
     SkPaint::FilterLevel paintFilterLevel = paint.getFilterLevel();
     GrTextureParams::FilterMode textureFilterMode;
     switch(paintFilterLevel) {
         case SkPaint::kNone_FilterLevel:
             textureFilterMode = GrTextureParams::kNone_FilterMode;
             break;
         case SkPaint::kLow_FilterLevel:
             textureFilterMode = GrTextureParams::kBilerp_FilterMode;
             break;
         case SkPaint::kMedium_FilterLevel:
             textureFilterMode = GrTextureParams::kMipMap_FilterMode;
             break;
         case SkPaint::kHigh_FilterLevel:
-            // fall back to no filtering here; we will install another
-            // shader that will do the HQ filtering.
-            textureFilterMode = GrTextureParams::kNone_FilterMode;
+            // Minification can look bad with the bicubic effect. This is an overly aggressive
+            // check for MIP fallbacks. It doesn't consider the fact that minification in the local
+            // matrix could be offset by the view matrix and vice versa. We also don't know whether
+            // the draw has explicit local coords (e.g. drawVertices) where the scale factor is
+            // unknown and varies.
+            if (context->getMatrix().getMinStretch() >= SK_Scalar1 &&
+                this->getLocalMatrix().getMaxStretch() <= SK_Scalar1) {
+                // fall back to no filtering here; we will install another
+                // shader that will do the HQ filtering.
+                textureFilterMode = GrTextureParams::kNone_FilterMode;
+            } else {
+                // Fall back to mip-mapping.
+                paintFilterLevel = SkPaint::kMedium_FilterLevel;
+                textureFilterMode = GrTextureParams::kMipMap_FilterMode;
+            }
             break;
         default:
             SkErrorInternals::SetError( kInvalidPaint_SkError,
                                         "Sorry, I don't understand the filtering "
                                         "mode you asked for.  Falling back to "
                                         "MIPMaps.");
             textureFilterMode = GrTextureParams::kMipMap_FilterMode;
             break;
 
     }
     GrTextureParams params(tm, textureFilterMode);
     GrTexture* texture = GrLockAndRefCachedBitmapTexture(context, fRawBitmap, &params);
 
     if (NULL == texture) {
         SkErrorInternals::SetError( kInternalError_SkError,
                                     "Couldn't convert bitmap to texture.");
         return NULL;
     }
 
     GrEffectRef* effect = NULL;
     if (paintFilterLevel == SkPaint::kHigh_FilterLevel) {
         effect = GrBicubicEffect::Create(texture, matrix, params);
     } else {
         effect = GrSimpleTextureEffect::Create(texture, matrix, params);
     }
     GrUnlockAndUnrefCachedBitmapTexture(texture);
     return effect;
 }
 #endif