A software implementation of the Gaussian blur filter, using 3 box blurs. Also

re-enable the imageblur GM test, since the SkPicture path now works.

Review URL:  http://codereview.appspot.com/5413048/



git-svn-id: http://skia.googlecode.com/svn/trunk@2905 2bbb7eff-a529-9590-31e7-b0007b416f81

gyp/gmslides.gypi

@@ -19,9 +19,7 @@
     '../gm/gradients.cpp',
     '../gm/gradtext.cpp',
     '../gm/hairmodes.cpp',
-#    commented out until SkPicture support for SkImageFilter is complete
-#    See http://code.google.com/p/skia/issues/detail?id=391
-#    '../gm/imageblur.cpp',
+    '../gm/imageblur.cpp',
     '../gm/lcdtext.cpp',
     '../gm/linepaths.cpp',
     '../gm/movepaths.cpp',

include/effects/SkBlurImageFilter.h

@@ -19,6 +19,9 @@ public:
         return SkNEW_ARGS(SkBlurImageFilter, (buffer));
     }
 
+    virtual bool onFilterImage(const SkBitmap& src, const SkMatrix&,
+                               SkBitmap* result, SkIPoint* offset);
+
     SK_DECLARE_FLATTENABLE_REGISTRAR()
 
 protected:

src/effects/SkBlurImageFilter.cpp

@@ -6,6 +6,7 @@
  */
 
 #include "SkBlurImageFilter.h"
+#include "SkColorPriv.h"
 
 SkBlurImageFilter::SkBlurImageFilter(SkFlattenableReadBuffer& buffer)
   : INHERITED(buffer) {
@@ -29,4 +30,153 @@ void SkBlurImageFilter::flatten(SkFlattenableWriteBuffer& buffer) {
     buffer.writeScalar(fSigma.fHeight);
 }
 
+static void boxBlurX(const SkBitmap& src, SkBitmap* dst, int kernelSize,
+                     int leftOffset, int rightOffset)
+{
+    int width = src.width(), height = src.height();
+    int rightBorder = SkMin32(rightOffset + 1, width);
+    for (int y = 0; y < height; ++y) {
+        int sumA = 0, sumR = 0, sumG = 0, sumB = 0;
+        SkPMColor* p = src.getAddr32(0, y);
+        for (int i = 0; i < rightBorder; ++i) {
+            sumA += SkGetPackedA32(*p);
+            sumR += SkGetPackedR32(*p);
+            sumG += SkGetPackedG32(*p);
+            sumB += SkGetPackedB32(*p);
+            p++;
+        }
+
+        const SkColor* sptr = src.getAddr32(0, y);
+        SkColor* dptr = dst->getAddr32(0, y);
+        for (int x = 0; x < width; ++x) {
+            *dptr = SkPackARGB32(sumA / kernelSize,
+                                 sumR / kernelSize,
+                                 sumG / kernelSize,
+                                 sumB / kernelSize);
+            if (x >= leftOffset) {
+                SkColor l = *(sptr - leftOffset);
+                sumA -= SkGetPackedA32(l);
+                sumR -= SkGetPackedR32(l);
+                sumG -= SkGetPackedG32(l);
+                sumB -= SkGetPackedB32(l);
+            }
+            if (x + rightOffset + 1 < width) {
+                SkColor r = *(sptr + rightOffset + 1);
+                sumA += SkGetPackedA32(r);
+                sumR += SkGetPackedR32(r);
+                sumG += SkGetPackedG32(r);
+                sumB += SkGetPackedB32(r);
+            }
+            sptr++;
+            dptr++;
+        }
+    }
+}
+
+static void boxBlurY(const SkBitmap& src, SkBitmap* dst, int kernelSize,
+                     int topOffset, int bottomOffset)
+{
+    int width = src.width(), height = src.height();
+    int bottomBorder = SkMin32(bottomOffset + 1, height);
+    int srcStride = src.rowBytesAsPixels();
+    int dstStride = dst->rowBytesAsPixels();
+    for (int x = 0; x < width; ++x) {
+        int sumA = 0, sumR = 0, sumG = 0, sumB = 0;
+        SkColor* p = src.getAddr32(x, 0);
+        for (int i = 0; i < bottomBorder; ++i) {
+            sumA += SkGetPackedA32(*p);
+            sumR += SkGetPackedR32(*p);
+            sumG += SkGetPackedG32(*p);
+            sumB += SkGetPackedB32(*p);
+            p += srcStride;
+        }
+
+        const SkColor* sptr = src.getAddr32(x, 0);
+        SkColor* dptr = dst->getAddr32(x, 0);
+        for (int y = 0; y < height; ++y) {
+            *dptr = SkPackARGB32(sumA / kernelSize,
+                                 sumR / kernelSize,
+                                 sumG / kernelSize,
+                                 sumB / kernelSize);
+            if (y >= topOffset) {
+                SkColor l = *(sptr - topOffset * srcStride);
+                sumA -= SkGetPackedA32(l);
+                sumR -= SkGetPackedR32(l);
+                sumG -= SkGetPackedG32(l);
+                sumB -= SkGetPackedB32(l);
+            }
+            if (y + bottomOffset + 1 < height) {
+                SkColor r = *(sptr + (bottomOffset + 1) * srcStride);
+                sumA += SkGetPackedA32(r);
+                sumR += SkGetPackedR32(r);
+                sumG += SkGetPackedG32(r);
+                sumB += SkGetPackedB32(r);
+            }
+            sptr += srcStride;
+            dptr += dstStride;
+        }
+    }
+}
+
+static void getBox3Params(SkScalar s, int *kernelSize, int* kernelSize3, int *lowOffset, int *highOffset)
+{
+    int d = static_cast<int>(floorf(SkScalarToFloat(s) * 3.0f * sqrtf(2.0f * M_PI) / 4.0f + 0.5f));
+    *kernelSize = d;
+    if (d % 2 == 1) {
+        *lowOffset = *highOffset = (d - 1) / 2;
+        *kernelSize3 = d;
+    } else {
+        *highOffset = d / 2;
+        *lowOffset = *highOffset - 1;
+        *kernelSize3 = d + 1;
+    }
+}
+
+bool SkBlurImageFilter::onFilterImage(const SkBitmap& src, const SkMatrix&,
+                                      SkBitmap* dst, SkIPoint*) {
+    if (src.config() != SkBitmap::kARGB_8888_Config) {
+        return false;
+    }
+
+    dst->setConfig(src.config(), src.width(), src.height());
+    dst->allocPixels();
+    int kernelSizeX, kernelSizeX3, lowOffsetX, highOffsetX;
+    int kernelSizeY, kernelSizeY3, lowOffsetY, highOffsetY;
+    getBox3Params(fSigma.width(), &kernelSizeX, &kernelSizeX3, &lowOffsetX, &highOffsetX);
+    getBox3Params(fSigma.height(), &kernelSizeY, &kernelSizeY3, &lowOffsetY, &highOffsetY);
+
+    if (kernelSizeX < 0 || kernelSizeY < 0) {
+        return false;
+    }
+
+    if (kernelSizeX == 0 && kernelSizeY == 0) {
+        src.copyTo(dst, dst->config());
+        return true;
+    }
+
+    SkBitmap temp;
+    temp.setConfig(dst->config(), dst->width(), dst->height());
+    if (!temp.allocPixels()) {
+        return false;
+    }
+
+    if (kernelSizeX > 0 && kernelSizeY > 0) {
+        boxBlurX(src,  &temp, kernelSizeX,  lowOffsetX, highOffsetX);
+        boxBlurY(temp, dst,   kernelSizeY,  lowOffsetY, highOffsetY);
+        boxBlurX(*dst, &temp, kernelSizeX,  highOffsetX,  lowOffsetX);
+        boxBlurY(temp, dst,   kernelSizeY,  highOffsetY,  lowOffsetY);
+        boxBlurX(*dst, &temp, kernelSizeX3, highOffsetX, highOffsetX);
+        boxBlurY(temp, dst,   kernelSizeY3, highOffsetY, highOffsetY);
+    } else if (kernelSizeX > 0) {
+        boxBlurX(src,  dst,   kernelSizeX,  lowOffsetX, highOffsetX);
+        boxBlurX(*dst, &temp, kernelSizeX,  highOffsetX,  lowOffsetX);
+        boxBlurX(temp, dst,   kernelSizeX3, highOffsetX, highOffsetX);
+    } else if (kernelSizeY > 0) {
+        boxBlurY(src,  dst,   kernelSizeY,  lowOffsetY, highOffsetY);
+        boxBlurY(*dst, &temp, kernelSizeY,  highOffsetY, lowOffsetY);
+        boxBlurY(temp, dst,   kernelSizeY3, highOffsetY, highOffsetY);
+    }
+    return true;
+}
+
 SK_DEFINE_FLATTENABLE_REGISTRAR(SkBlurImageFilter)