Avoid creating MIPs until necessary when MIP bias is active

With sharpened mips, the scale at which we begin to sample level 1 is
(obviously) less than 1. This change avoids creation of mips for images
that are only slightly downscaled (and for which we wouldn't have sampled
those MIPs anyway).

Change-Id: If8ffc79c2ce2ff1f3aae7f5732d8a50aca0e26be
Reviewed-on: https://skia-review.googlesource.com/107801
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

5 files changed, 26 insertions, 8 deletions

diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 7521278fac..9a01394691 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -761,8 +761,9 @@ bool SkGpuDevice::shouldTileImage(const SkImage* image, const SkRect* srcRectPtr
 
     GrSamplerState samplerState;
     bool doBicubic;
-    GrSamplerState::Filter textureFilterMode =
-            GrSkFilterQualityToGrFilterMode(quality, viewMatrix, srcToDstRect, &doBicubic);
+    GrSamplerState::Filter textureFilterMode = GrSkFilterQualityToGrFilterMode(
+            quality, viewMatrix, srcToDstRect, fContext->contextPriv().sharpenMipmappedTextures(),
+            &doBicubic);
 
     int tileFilterPad;
     if (doBicubic) {
@@ -812,7 +813,8 @@ void SkGpuDevice::drawBitmap(const SkBitmap& bitmap,
         GrSamplerState samplerState;
         bool doBicubic;
         GrSamplerState::Filter textureFilterMode = GrSkFilterQualityToGrFilterMode(
-                paint.getFilterQuality(), viewMatrix, SkMatrix::I(), &doBicubic);
+                paint.getFilterQuality(), viewMatrix, SkMatrix::I(),
+                fContext->contextPriv().sharpenMipmappedTextures(), &doBicubic);
 
         int tileFilterPad;
 
@@ -1170,7 +1172,8 @@ void SkGpuDevice::drawBitmapRect(const SkBitmap& bitmap,
         GrSamplerState sampleState;
         bool doBicubic;
         GrSamplerState::Filter textureFilterMode = GrSkFilterQualityToGrFilterMode(
-                paint.getFilterQuality(), this->ctm(), srcToDstMatrix, &doBicubic);
+                paint.getFilterQuality(), this->ctm(), srcToDstMatrix,
+                fContext->contextPriv().sharpenMipmappedTextures(), &doBicubic);
 
         int tileFilterPad;
 
@@ -1362,7 +1365,8 @@ void SkGpuDevice::drawProducerNine(GrTextureProducer* producer,
                        GrFSAAType::kUnifiedMSAA == fRenderTargetContext->fsaaType();
     bool doBicubic;
     GrSamplerState::Filter textureFilterMode = GrSkFilterQualityToGrFilterMode(
-            paint.getFilterQuality(), this->ctm(), SkMatrix::I(), &doBicubic);
+            paint.getFilterQuality(), this->ctm(), SkMatrix::I(),
+            fContext->contextPriv().sharpenMipmappedTextures(), &doBicubic);
     if (useFallback || doBicubic || GrSamplerState::Filter::kNearest != textureFilterMode) {
         SkLatticeIter iter(producer->width(), producer->height(), center, dst);
 
diff --git a/src/gpu/SkGpuDevice_drawTexture.cpp b/src/gpu/SkGpuDevice_drawTexture.cpp
index b6b1e619c0..c91d7a4569 100644
--- a/src/gpu/SkGpuDevice_drawTexture.cpp
+++ b/src/gpu/SkGpuDevice_drawTexture.cpp
@@ -258,7 +258,8 @@ void SkGpuDevice::drawTextureProducerImpl(GrTextureProducer* producer,
 
     bool doBicubic;
     GrSamplerState::Filter fm = GrSkFilterQualityToGrFilterMode(
-            paint.getFilterQuality(), viewMatrix, srcToDstMatrix, &doBicubic);
+            paint.getFilterQuality(), viewMatrix, srcToDstMatrix,
+            fContext->contextPriv().sharpenMipmappedTextures(), &doBicubic);
     const GrSamplerState::Filter* filterMode = doBicubic ? nullptr : &fm;
 
     GrTextureProducer::FilterConstraint constraintMode;
diff --git a/src/gpu/SkGr.cpp b/src/gpu/SkGr.cpp
index 12e7670029..c4bbf487f8 100644
--- a/src/gpu/SkGr.cpp
+++ b/src/gpu/SkGr.cpp
@@ -562,6 +562,7 @@ bool SkPaintToGrPaintWithTexture(GrContext* context,
 GrSamplerState::Filter GrSkFilterQualityToGrFilterMode(SkFilterQuality paintFilterQuality,
                                                        const SkMatrix& viewM,
                                                        const SkMatrix& localM,
+                                                       bool sharpenMipmappedTextures,
                                                        bool* doBicubic) {
     *doBicubic = false;
     GrSamplerState::Filter textureFilterMode;
@@ -575,7 +576,16 @@ GrSamplerState::Filter GrSkFilterQualityToGrFilterMode(SkFilterQuality paintFilt
         case kMedium_SkFilterQuality: {
             SkMatrix matrix;
             matrix.setConcat(viewM, localM);
-            if (matrix.getMinScale() < SK_Scalar1) {
+            // With sharp mips, we bias lookups by -0.5. That means our final LOD is >= 0 until the
+            // computed LOD is >= 0.5. At what scale factor does a texture get an LOD of 0.5?
+            //
+            // Want:  0       = log2(1/s) - 0.5
+            //        0.5     = log2(1/s)
+            //        2^0.5   = 1/s
+            //        1/2^0.5 = s
+            //        2^0.5/2 = s
+            SkScalar mipScale = sharpenMipmappedTextures ? SK_ScalarRoot2Over2 : SK_Scalar1;
+            if (matrix.getMinScale() < mipScale) {
                 textureFilterMode = GrSamplerState::Filter::kMipMap;
             } else {
                 // Don't trigger MIP level generation unnecessarily.
diff --git a/src/gpu/SkGr.h b/src/gpu/SkGr.h
index 5657821cbe..fc0aa63d4a 100644
--- a/src/gpu/SkGr.h
+++ b/src/gpu/SkGr.h
@@ -152,6 +152,7 @@ bool GrPixelConfigToColorType(GrPixelConfig, SkColorType*);
 GrSamplerState::Filter GrSkFilterQualityToGrFilterMode(SkFilterQuality paintFilterQuality,
                                                        const SkMatrix& viewM,
                                                        const SkMatrix& localM,
+                                                       bool sharpenMipmappedTextures,
                                                        bool* doBicubic);
 
 //////////////////////////////////////////////////////////////////////////////
diff --git a/src/shaders/SkImageShader.cpp b/src/shaders/SkImageShader.cpp
index debd13b2ef..9f39fe2792 100644
--- a/src/shaders/SkImageShader.cpp
+++ b/src/shaders/SkImageShader.cpp
@@ -201,6 +201,7 @@ void SkImageShader::toString(SkString* str) const {
 
 #include "GrColorSpaceInfo.h"
 #include "GrContext.h"
+#include "GrContextPriv.h"
 #include "SkGr.h"
 #include "effects/GrBicubicEffect.h"
 #include "effects/GrSimpleTextureEffect.h"
@@ -243,7 +244,8 @@ std::unique_ptr<GrFragmentProcessor> SkImageShader::asFragmentProcessor(
     // are provided by the caller.
     bool doBicubic;
     GrSamplerState::Filter textureFilterMode = GrSkFilterQualityToGrFilterMode(
-            args.fFilterQuality, *args.fViewMatrix, lm, &doBicubic);
+            args.fFilterQuality, *args.fViewMatrix, lm,
+            args.fContext->contextPriv().sharpenMipmappedTextures(), &doBicubic);
     GrSamplerState samplerState(wrapModes, textureFilterMode);
     sk_sp<SkColorSpace> texColorSpace;
     SkScalar scaleAdjust[2] = { 1.0f, 1.0f };