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Added support for optimised reference image PNGs
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This allows to use apps like ImageOptim.app to optimise recorded
reference images. Optimising reference image can heavily reduce
its size, meaning we need to store less binary data in repo.
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@lukaskukacka
lukaskukacka committed Aug 30, 2021
1 parent 6be2bd7 commit 3fa343c
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Showing 6 changed files with 55 additions and 11 deletions.
12 changes: 12 additions & 0 deletions FBSnapshotTestCase.xcodeproj/project.pbxproj
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Expand Up @@ -36,6 +36,10 @@
827137A21C63AC0D00354E42 /* square-copy.png in Resources */ = {isa = PBXBuildFile; fileRef = B32447DA1AB78B5E00B1D6FF /* square-copy.png */; };
827137A31C63AC0D00354E42 /* square.png in Resources */ = {isa = PBXBuildFile; fileRef = B32447DB1AB78B5E00B1D6FF /* square.png */; };
827137A41C63AC0F00354E42 /* FBSnapshotControllerTests.m in Sources */ = {isa = PBXBuildFile; fileRef = B31988301AB784CB00B0A900 /* FBSnapshotControllerTests.m */; };
A9E093ED2261EEA400B1EDE3 /* square_with_graphics_imageoptim.png in Resources */ = {isa = PBXBuildFile; fileRef = A9E093EB2261EEA300B1EDE3 /* square_with_graphics_imageoptim.png */; };
A9E093EE2261EEA400B1EDE3 /* square_with_graphics_imageoptim.png in Resources */ = {isa = PBXBuildFile; fileRef = A9E093EB2261EEA300B1EDE3 /* square_with_graphics_imageoptim.png */; };
A9E093EF2261EEA400B1EDE3 /* square_with_graphics.png in Resources */ = {isa = PBXBuildFile; fileRef = A9E093EC2261EEA400B1EDE3 /* square_with_graphics.png */; };
A9E093F02261EEA400B1EDE3 /* square_with_graphics.png in Resources */ = {isa = PBXBuildFile; fileRef = A9E093EC2261EEA400B1EDE3 /* square_with_graphics.png */; };
B31987FC1AB782D100B0A900 /* FBSnapshotTestCase.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = B31987F01AB782D000B0A900 /* FBSnapshotTestCase.framework */; };
B31988281AB7849400B0A900 /* FBSnapshotTestCase.h in Headers */ = {isa = PBXBuildFile; fileRef = B31988201AB7849400B0A900 /* FBSnapshotTestCase.h */; settings = {ATTRIBUTES = (Public, ); }; };
B31988291AB7849400B0A900 /* FBSnapshotTestCase.m in Sources */ = {isa = PBXBuildFile; fileRef = B31988211AB7849400B0A900 /* FBSnapshotTestCase.m */; };
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42F2B74320C0D7A400ABED24 /* rect_shade.png */ = {isa = PBXFileReference; lastKnownFileType = image.png; path = rect_shade.png; sourceTree = "<group>"; };
8271377A1C63AB6F00354E42 /* FBSnapshotTestCase.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = FBSnapshotTestCase.framework; sourceTree = BUILT_PRODUCTS_DIR; };
827137831C63AB7000354E42 /* FBSnapshotTestCase tvOS Tests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = "FBSnapshotTestCase tvOS Tests.xctest"; sourceTree = BUILT_PRODUCTS_DIR; };
A9E093EB2261EEA300B1EDE3 /* square_with_graphics_imageoptim.png */ = {isa = PBXFileReference; lastKnownFileType = image.png; path = square_with_graphics_imageoptim.png; sourceTree = "<group>"; };
A9E093EC2261EEA400B1EDE3 /* square_with_graphics.png */ = {isa = PBXFileReference; lastKnownFileType = image.png; path = square_with_graphics.png; sourceTree = "<group>"; };
B31987F01AB782D000B0A900 /* FBSnapshotTestCase.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = FBSnapshotTestCase.framework; sourceTree = BUILT_PRODUCTS_DIR; };
B31987F41AB782D000B0A900 /* FBSnapshotTestCase-Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = "FBSnapshotTestCase-Info.plist"; sourceTree = "<group>"; };
B31987FB1AB782D100B0A900 /* FBSnapshotTestCase iOS Tests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = "FBSnapshotTestCase iOS Tests.xctest"; sourceTree = BUILT_PRODUCTS_DIR; };
Expand Down Expand Up @@ -196,6 +202,8 @@
children = (
42F2B74320C0D7A400ABED24 /* rect_shade.png */,
B76C68271C6BD68100586E5B /* rect.png */,
A9E093EB2261EEA300B1EDE3 /* square_with_graphics_imageoptim.png */,
A9E093EC2261EEA400B1EDE3 /* square_with_graphics.png */,
E5C2CD611B1F399A00669887 /* square_with_pixel.png */,
B32447D91AB78B5E00B1D6FF /* square_with_text.png */,
B32447DA1AB78B5E00B1D6FF /* square-copy.png */,
Expand Down Expand Up @@ -380,11 +388,13 @@
buildActionMask = 2147483647;
files = (
B76C682A1C6BD6D500586E5B /* rect.png in Resources */,
A9E093EE2261EEA400B1EDE3 /* square_with_graphics_imageoptim.png in Resources */,
827137A01C63AC0700354E42 /* square_with_pixel.png in Resources */,
827137A21C63AC0D00354E42 /* square-copy.png in Resources */,
827137A31C63AC0D00354E42 /* square.png in Resources */,
827137A11C63AC0900354E42 /* square_with_text.png in Resources */,
42F2B74520C0D7A400ABED24 /* rect_shade.png in Resources */,
A9E093F02261EEA400B1EDE3 /* square_with_graphics.png in Resources */,
);
runOnlyForDeploymentPostprocessing = 0;
};
Expand All @@ -400,11 +410,13 @@
buildActionMask = 2147483647;
files = (
B76C68291C6BD6D200586E5B /* rect.png in Resources */,
A9E093ED2261EEA400B1EDE3 /* square_with_graphics_imageoptim.png in Resources */,
B32447DC1AB78B5E00B1D6FF /* square_with_text.png in Resources */,
E5C2CD621B1F399A00669887 /* square_with_pixel.png in Resources */,
B32447DE1AB78B5E00B1D6FF /* square.png in Resources */,
B32447DD1AB78B5E00B1D6FF /* square-copy.png in Resources */,
42F2B74420C0D7A400ABED24 /* rect_shade.png in Resources */,
A9E093EF2261EEA400B1EDE3 /* square_with_graphics.png in Resources */,
);
runOnlyForDeploymentPostprocessing = 0;
};
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31 changes: 20 additions & 11 deletions FBSnapshotTestCase/Categories/UIImage+Compare.m
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Expand Up @@ -50,9 +50,15 @@ - (BOOL)fb_compareWithImage:(UIImage *)image perPixelTolerance:(CGFloat)perPixel
CGSize imageSize = CGSizeMake(CGImageGetWidth(image.CGImage), CGImageGetHeight(image.CGImage));
NSAssert(CGSizeEqualToSize(referenceImageSize, imageSize), @"Images must be same size.");

// The images have the equal size, so we could use the smallest amount of bytes because of byte padding
size_t minBytesPerRow = MIN(CGImageGetBytesPerRow(self.CGImage), CGImageGetBytesPerRow(image.CGImage));
size_t referenceImageSizeBytes = referenceImageSize.height * minBytesPerRow;
// Find image which requires more bytes in memory. We have to normalise both images to context requiring "bigger" memory representation.
// This allows comparing 2 visually identical images even if their bit representation in file can be different
// (for example reference images optimised using ImageOptim app).
// Because both images have the same pixel size, image with more bytes per row is the image dictating the context config for comparison.
UIImage *contextConfigImage = (CGImageGetBytesPerRow(image.CGImage) > CGImageGetBytesPerRow(self.CGImage) ? image : self);

// Create contexts for both images using the same configuration.
size_t bytesPerRow = CGImageGetBytesPerRow(contextConfigImage.CGImage);
size_t referenceImageSizeBytes = referenceImageSize.height * bytesPerRow;
void *referenceImagePixels = calloc(1, referenceImageSizeBytes);
void *imagePixels = calloc(1, referenceImageSizeBytes);

Expand All @@ -62,20 +68,23 @@ - (BOOL)fb_compareWithImage:(UIImage *)image perPixelTolerance:(CGFloat)perPixel
return NO;
}

size_t bitsPerComponent = CGImageGetBitsPerComponent(contextConfigImage.CGImage);
CGBitmapInfo bitmapInfo = (CGBitmapInfo)kCGImageAlphaPremultipliedLast;

CGContextRef referenceImageContext = CGBitmapContextCreate(referenceImagePixels,
referenceImageSize.width,
referenceImageSize.height,
CGImageGetBitsPerComponent(self.CGImage),
minBytesPerRow,
CGImageGetColorSpace(self.CGImage),
(CGBitmapInfo)kCGImageAlphaPremultipliedLast);
bitsPerComponent,
bytesPerRow,
CGImageGetColorSpace(contextConfigImage.CGImage),
bitmapInfo);
CGContextRef imageContext = CGBitmapContextCreate(imagePixels,
imageSize.width,
imageSize.height,
CGImageGetBitsPerComponent(image.CGImage),
minBytesPerRow,
CGImageGetColorSpace(image.CGImage),
(CGBitmapInfo)kCGImageAlphaPremultipliedLast);
bitsPerComponent,
bytesPerRow,
CGImageGetColorSpace(contextConfigImage.CGImage),
bitmapInfo);

if (!referenceImageContext || !imageContext) {
CGContextRelease(referenceImageContext);
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14 changes: 14 additions & 0 deletions FBSnapshotTestCaseTests/FBSnapshotControllerTests.m
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Expand Up @@ -48,6 +48,20 @@ - (void)testCompareReferenceImageToImageShouldNotBeEqual
XCTAssertEqual(error.code, FBSnapshotTestControllerErrorCodeImagesDifferent);
}

- (void)testCompareOptimisedReferenceImageToImageShouldBeEqual
{
UIImage *referenceImage = [self _bundledImageNamed:@"square_with_graphics_imageoptim" type:@"png"];
XCTAssertNotNil(referenceImage);
UIImage *testImage = [self _bundledImageNamed:@"square_with_graphics" type:@"png"];
XCTAssertNotNil(testImage);

id testClass = nil;
FBSnapshotTestController *controller = [[FBSnapshotTestController alloc] initWithTestClass:testClass];
NSError *error = nil;
XCTAssertTrue([controller compareReferenceImage:referenceImage toImage:testImage overallTolerance:0 error:&error]);
XCTAssertNil(error);
}

- (void)testCompareReferenceImageWithVeryLowToleranceShouldNotMatch
{
UIImage *referenceImage = [self _bundledImageNamed:@"square" type:@"png"];
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Binary file added FBSnapshotTestCaseTests/square_with_graphics.png
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Binary file added FBSnapshotTestCaseTests/square_with_graphics_imageoptim.png
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9 changes: 9 additions & 0 deletions README.md
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Expand Up @@ -85,6 +85,7 @@ Define the `IMAGE_DIFF_DIR` to the directory where you want to store diffs of fa
- Support for `CALayer` via `FBSnapshotVerifyLayer`.
- `usesDrawViewHierarchyInRect` to handle cases like `UIVisualEffect`, `UIAppearance` and Size Classes.
- `fileNameOptions` to control appending the device model (`iPhone`, `iPad`, `iPod Touch`, etc), OS version, screen size and screen scale to the images (allowing to have multiple tests for the same «snapshot» for different `OS`s and devices).
- Support of reference images optimized for reduced size.

## Notes

Expand All @@ -95,6 +96,14 @@ should be run within the Simulator so that it has access to UIKit.)

Read more on this [here](docs/LibraryVsApplicationTestBundles.md).

## Optimizing reference images to reduce size

Recorded reference image PNG can be optimised to reduce its size using lossless compression.

Once you have final reference images recorded, you can manually optimise them using tools like [ImageOptim](https://imageoptim.com). ImageOptim will reduce size of the image without loss of any visual information. The savings in image sizes can be significant (up to 80%+ depending on the original image).

If you are committing reference images to repository, optimizing them reduces their impact growing to repo size.

## Authors

`iOSSnapshotTestCase` was written at Facebook by
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