improve convolve speed of skpdiff using direct pointers
R=djsollen@google.com
Review URL: https://codereview.chromium.org/19107002
git-svn-id: http://skia.googlecode.com/svn/trunk@10099 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/experimental/skpdiff/SkPMetric.cpp b/experimental/skpdiff/SkPMetric.cpp
index a962853..c68646c 100644
--- a/experimental/skpdiff/SkPMetric.cpp
+++ b/experimental/skpdiff/SkPMetric.cpp
@@ -38,6 +38,10 @@
*pixel = image[y * width + x];
}
+ T* getRow(int y) const {
+ return &image[y * width];
+ }
+
void writePixel(int x, int y, const T& pixel) {
SkASSERT(x >= 0);
SkASSERT(y >= 0);
@@ -191,15 +195,25 @@
}
/// Convolves an image with the given filter in one direction and saves it to the output image
-static void convolve(const ImageL* imageL,
- bool vertical, const float* matrix, int radius,
- ImageL* outImageL) {
+static void convolve(const ImageL* imageL, bool vertical, ImageL* outImageL) {
SkASSERT(imageL->width == outImageL->width);
SkASSERT(imageL->height == outImageL->height);
+
+ const float matrix[] = { 0.05f, 0.25f, 0.4f, 0.25f, 0.05f };
+ const int matrixCount = sizeof(matrix) / sizeof(float);
+ const int radius = matrixCount / 2;
+
+ // Keep track of what rows are being operated on for quick access.
+ float* rowPtrs[matrixCount]; // Because matrixCount is constant, this won't create a VLA
+ for (int y = radius; y < matrixCount; y++) {
+ rowPtrs[y] = imageL->getRow(y - radius);
+ }
+ float* writeRow = outImageL->getRow(0);
+
+
for (int y = 0; y < imageL->height; y++) {
for (int x = 0; x < imageL->width; x++) {
float lSum = 0.0f;
- float l;
for (int xx = -radius; xx <= radius; xx++) {
int nx = x;
int ny = y;
@@ -224,12 +238,18 @@
}
}
- imageL->readPixel(nx, ny, &l);
float weight = matrix[xx + radius];
- lSum += l * weight;
+ lSum += rowPtrs[ny - y + radius][nx] * weight;
}
- outImageL->writePixel(x, y, lSum);
+ writeRow[x] = lSum;
}
+ // As we move down, scroll the row pointers down with us
+ for (int y = 0; y < matrixCount - 1; y++)
+ {
+ rowPtrs[y] = rowPtrs[y + 1];
+ }
+ rowPtrs[matrixCount - 1] += imageL->width;
+ writeRow += imageL->width;
}
}
@@ -258,15 +278,14 @@
cyclesPerDegree[levelIndex] = cyclesPerDegree[levelIndex - 1] * 0.5f;
}
- const float filterMatrix[] = { 0.05f, 0.25f, 0.4f, 0.25f, 0.05f };
// Compute G - The convolved lum for the baseline
for (int levelIndex = 1; levelIndex < maxLevels; levelIndex++) {
- convolve(baselineL.getLayer(levelIndex - 1), false, filterMatrix, 2, &scratchImageL);
- convolve(&scratchImageL, true, filterMatrix, 2, baselineL.getLayer(levelIndex));
+ convolve(baselineL.getLayer(levelIndex - 1), false, &scratchImageL);
+ convolve(&scratchImageL, true, baselineL.getLayer(levelIndex));
}
for (int levelIndex = 1; levelIndex < maxLevels; levelIndex++) {
- convolve(testL.getLayer(levelIndex - 1), false, filterMatrix, 2, &scratchImageL);
- convolve(&scratchImageL, true, filterMatrix, 2, testL.getLayer(levelIndex));
+ convolve(testL.getLayer(levelIndex - 1), false, &scratchImageL);
+ convolve(&scratchImageL, true, testL.getLayer(levelIndex));
}
// Compute F_freq - The elevation f