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Perform fast memcmp comparison before making deep pixel-by-pixel comparison #142

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Perform fast memcmp comparison before making deep pixel-by-pixel comparison #142

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Perform fast comparison first.
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Constantine Fry committed Feb 25, 2021
commit 4ba3791f10c1bf0fb686c7c1d53610899d2cd643
22 changes: 11 additions & 11 deletions FBSnapshotTestCase/Categories/UIImage+Compare.m
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Original file line number Diff line number Diff line change
Expand Up @@ -91,21 +91,21 @@ - (BOOL)fb_compareWithImage:(UIImage *)image perPixelTolerance:(CGFloat)perPixel
CGContextRelease(referenceImageContext);
CGContextRelease(imageContext);

BOOL imageEqual = YES;
FBComparePixel *p1 = referenceImagePixels;
FBComparePixel *p2 = imagePixels;

BOOL imageEqual = (memcmp(referenceImagePixels, imagePixels, referenceImageSizeBytes) == 0);
// Do a fast compare if we can
if (overallTolerance == 0 && perPixelTolerance == 0) {
imageEqual = (memcmp(referenceImagePixels, imagePixels, referenceImageSizeBytes) == 0);
} else {
const NSUInteger pixelCount = referenceImageSize.width * referenceImageSize.height;
// Go through each pixel in turn and see if it is different
imageEqual = [self _compareAllPixelsWithPerPixelTolerance:perPixelTolerance
overallTolerance:overallTolerance
pixelCount:pixelCount
referencePixels:p1
imagePixels:p2];
if (!imageEqual) {
if (overallTolerance != 0 || perPixelTolerance != 0) {
const NSUInteger pixelCount = referenceImageSize.width * referenceImageSize.height;
// Go through each pixel in turn and see if it is different
imageEqual = [self _compareAllPixelsWithPerPixelTolerance:perPixelTolerance
overallTolerance:overallTolerance
pixelCount:pixelCount
referencePixels:p1
imagePixels:p2];
}
}

free(referenceImagePixels);
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