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DM: find max component difference

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So far unused except to back BitmapsEqual, but I want to play with it in CLs I'm working on.

BUG=skia:
R=reed@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/290043005

git-svn-id: http://skia.googlecode.com/svn/trunk@14759 2bbb7eff-a529-9590-31e7-b0007b416f81
This commit is contained in:
commit-bot@chromium.org 2014-05-16 13:03:46 +00:00
parent f9b4a00a92
commit 69031a4427
2 changed files with 49 additions and 2 deletions
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48
dm/DMUtil.cpp
View File

@ -1,5 +1,6 @@
#include "DMUtil.h"
#include "SkColorPriv.h"
#include "SkPicture.h"
#include "SkPictureRecorder.h"
@ -38,9 +39,52 @@ void DrawPicture(SkPicture* picture, SkBitmap* bitmap) {
canvas.flush();
}
bool BitmapsEqual(const SkBitmap& a, const SkBitmap& b) {
static void unpack_565(uint16_t pixel, unsigned* r, unsigned* g, unsigned* b) {
*r = SkGetPackedR16(pixel);
*g = SkGetPackedG16(pixel);
*b = SkGetPackedB16(pixel);
}
// Returns |a-b|.
static unsigned abs_diff(unsigned a, unsigned b) {
return a > b ? a - b : b - a;
}
unsigned MaxComponentDifference(const SkBitmap& a, const SkBitmap& b) {
if (a.info() != b.info()) {
SkFAIL("Can't compare bitmaps of different shapes.");
}
unsigned max = 0;
const SkAutoLockPixels lockA(a), lockB(b);
return a.getSize() == b.getSize() && 0 == memcmp(a.getPixels(), b.getPixels(), b.getSize());
if (a.info().colorType() == kRGB_565_SkColorType) {
// 565 is special/annoying because its 3 components straddle 2 bytes.
const uint16_t* aPixels = (const uint16_t*)a.getPixels();
const uint16_t* bPixels = (const uint16_t*)b.getPixels();
for (size_t i = 0; i < a.getSize() / 2; i++) {
unsigned ar, ag, ab,
br, bg, bb;
unpack_565(aPixels[i], &ar, &ag, &ab);
unpack_565(bPixels[i], &br, &bg, &bb);
max = SkTMax(max, abs_diff(ar, br));
max = SkTMax(max, abs_diff(ag, bg));
max = SkTMax(max, abs_diff(ab, bb));
}
} else {
// Everything else we produce is byte aligned, so max component diff == max byte diff.
const uint8_t* aBytes = (const uint8_t*)a.getPixels();
const uint8_t* bBytes = (const uint8_t*)b.getPixels();
for (size_t i = 0; i < a.getSize(); i++) {
max = SkTMax(max, abs_diff(aBytes[i], bBytes[i]));
}
}
return max;
}
bool BitmapsEqual(const SkBitmap& a, const SkBitmap& b) {
return a.info() == b.info() && 0 == MaxComponentDifference(a, b);
}
} // namespace DM

3
dm/DMUtil.h
View File

@ -28,6 +28,9 @@ void AllocatePixels(const SkBitmap& reference, SkBitmap* bitmap);
// Draw picture to bitmap.
void DrawPicture(SkPicture* picture, SkBitmap* bitmap);
// What is the maximum component difference in these bitmaps?
unsigned MaxComponentDifference(const SkBitmap& a, const SkBitmap& b);
// Are these identical bitmaps?
bool BitmapsEqual(const SkBitmap& a, const SkBitmap& b);