Add support for non-standard content/images scales

FBSnapshotTestCase/Categories/UIImage+Compare.m

@@ -46,11 +46,11 @@ @implementation UIImage (Compare)
 
 - (BOOL)fb_compareWithImage:(UIImage *)image tolerance:(CGFloat)tolerance
 {
-  NSAssert(CGSizeEqualToSize(self.size, image.size), @"Images must be same size.");
-
   CGSize referenceImageSize = CGSizeMake(CGImageGetWidth(self.CGImage), CGImageGetHeight(self.CGImage));
   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;

FBSnapshotTestCase/Categories/UIImage+Diff.m

@@ -38,7 +38,7 @@ - (UIImage *)fb_diffWithImage:(UIImage *)image
     return nil;
   }
   CGSize imageSize = CGSizeMake(MAX(self.size.width, image.size.width), MAX(self.size.height, image.size.height));
-  UIGraphicsBeginImageContextWithOptions(imageSize, YES, 0);
+  UIGraphicsBeginImageContextWithOptions(imageSize, YES, self.scale);
   CGContextRef context = UIGraphicsGetCurrentContext();
   [self drawInRect:CGRectMake(0, 0, self.size.width, self.size.height)];
   CGContextSetAlpha(context, 0.5);

FBSnapshotTestCase/Categories/UIImage+Snapshot.h

@@ -13,12 +13,12 @@
 @interface UIImage (Snapshot)
 
 /// Uses renderInContext: to get a snapshot of the layer.
-+ (UIImage *)fb_imageForLayer:(CALayer *)layer;
++ (UIImage *)fb_imageForLayer:(CALayer *)layer scale:(CGFloat)scale;
 
 /// Uses renderInContext: to get a snapshot of the view layer.
-+ (UIImage *)fb_imageForViewLayer:(UIView *)view;
++ (UIImage *)fb_imageForViewLayer:(UIView *)view scale:(CGFloat)scale;
 
 /// Uses drawViewHierarchyInRect: to get a snapshot of the view and adds the view into a window if needed.
-+ (UIImage *)fb_imageForView:(UIView *)view;
++ (UIImage *)fb_imageForView:(UIView *)view scale:(CGFloat)scale;
 
 @end

FBSnapshotTestCase/Categories/UIImage+Snapshot.m

@@ -13,13 +13,13 @@
 
 @implementation UIImage (Snapshot)
 
-+ (UIImage *)fb_imageForLayer:(CALayer *)layer
++ (UIImage *)fb_imageForLayer:(CALayer *)layer scale:(CGFloat)scale
 {
   CGRect bounds = layer.bounds;
   NSAssert1(CGRectGetWidth(bounds), @"Zero width for layer %@", layer);
   NSAssert1(CGRectGetHeight(bounds), @"Zero height for layer %@", layer);
 
-  UIGraphicsBeginImageContextWithOptions(bounds.size, NO, 0);
+  UIGraphicsBeginImageContextWithOptions(bounds.size, NO, scale);
   CGContextRef context = UIGraphicsGetCurrentContext();
   NSAssert1(context, @"Could not generate context for layer %@", layer);
   CGContextSaveGState(context);
@@ -32,13 +32,13 @@ + (UIImage *)fb_imageForLayer:(CALayer *)layer
   return snapshot;
 }
 
-+ (UIImage *)fb_imageForViewLayer:(UIView *)view
++ (UIImage *)fb_imageForViewLayer:(UIView *)view scale:(CGFloat)scale
 {
   [view layoutIfNeeded];
-  return [self fb_imageForLayer:view.layer];
+  return [self fb_imageForLayer:view.layer scale:scale];
 }
 
-+ (UIImage *)fb_imageForView:(UIView *)view
++ (UIImage *)fb_imageForView:(UIView *)view scale:(CGFloat)scale
 {
   CGRect bounds = view.bounds;
   NSAssert1(CGRectGetWidth(bounds), @"Zero width for view %@", view);
@@ -56,7 +56,7 @@ + (UIImage *)fb_imageForView:(UIView *)view
     removeFromSuperview = YES;
   }
 
-  UIGraphicsBeginImageContextWithOptions(bounds.size, NO, 0);
+  UIGraphicsBeginImageContextWithOptions(bounds.size, NO, scale);
   [view layoutIfNeeded];
   [view drawViewHierarchyInRect:view.bounds afterScreenUpdates:YES];
 

FBSnapshotTestCase/FBSnapshotTestCase.h

@@ -145,6 +145,11 @@
  */
 @property (readwrite, nonatomic, assign) BOOL usesDrawViewHierarchyInRect;
 
+/**
+ When set to values different than 0, it uses a specific scale for generating and comparing images rather than using the main screen's default scale.
+ */
+@property (readwrite, nonatomic, assign) NSUInteger manualScale;
+
 - (void)setUp NS_REQUIRES_SUPER;
 - (void)tearDown NS_REQUIRES_SUPER;
 

FBSnapshotTestCase/FBSnapshotTestCase.m

@@ -63,6 +63,17 @@ - (void)setUsesDrawViewHierarchyInRect:(BOOL)usesDrawViewHierarchyInRect
   _snapshotController.usesDrawViewHierarchyInRect = usesDrawViewHierarchyInRect;
 }
 
+- (void)setManualScale:(NSUInteger)manualScale
+{
+  NSAssert1(_snapshotController, @"%s cannot be called before [super setUp]", __FUNCTION__);
+  _snapshotController.manualScale = manualScale;
+}
+
+- (NSUInteger)manualScale
+{
+  return _snapshotController.manualScale;
+}
+
 #pragma mark - Public API
 
 - (BOOL)compareSnapshotOfLayer:(CALayer *)layer
@@ -116,7 +127,6 @@ - (NSString *)getReferenceImageDirectoryWithDefault:(NSString *)dir
   return [[NSBundle bundleForClass:self.class].resourcePath stringByAppendingPathComponent:@"ReferenceImages"];
 }
 
-
 #pragma mark - Private API
 
 - (BOOL)_compareSnapshotOfViewOrLayer:(id)viewOrLayer

FBSnapshotTestCase/FBSnapshotTestController.h

@@ -71,6 +71,11 @@ extern NSString *const FBDiffedImageKey;
  */
 @property (readwrite, nonatomic, copy) NSString *referenceImagesDirectory;
 
+/**
+ When set to values different than 0, it uses a specific scale for generating and comparing images rather than using the main screen's default scale.
+ */
+@property (readwrite, nonatomic, assign) NSUInteger manualScale;
+
 /**
  @param testClass The subclass of FBSnapshotTestCase that is using this controller.
  @returns An instance of FBSnapshotTestController.

FBSnapshotTestCase/FBSnapshotTestController.m

@@ -105,7 +105,8 @@ - (UIImage *)referenceImageForSelector:(SEL)selector
 {
   NSString *filePath = [self _referenceFilePathForSelector:selector identifier:identifier];
   UIImage *image = [UIImage imageWithContentsOfFile:filePath];
-  if (nil == image && NULL != errorPtr) {
+  CGFloat scale = (self.manualScale > 0 ? self.manualScale : [[UIScreen mainScreen] scale]);
+  if ((nil == image && NULL != errorPtr) || (image && image.scale != scale)) {
     BOOL exists = [_fileManager fileExistsAtPath:filePath];
     if (!exists) {
       *errorPtr = [NSError errorWithDomain:FBSnapshotTestControllerErrorDomain
@@ -129,15 +130,21 @@ - (BOOL)compareReferenceImage:(UIImage *)referenceImage
                     tolerance:(CGFloat)tolerance
                         error:(NSError **)errorPtr
 {
-  BOOL sameImageDimensions = CGSizeEqualToSize(referenceImage.size, image.size);
+  CGSize referenceImagePixelSize = referenceImage.size;
+  referenceImagePixelSize = CGSizeMake(referenceImagePixelSize.width * referenceImage.scale,
+                                       referenceImagePixelSize.height * referenceImage.scale);
+  CGSize imagePixelSize = image.size;
+  imagePixelSize = CGSizeMake(imagePixelSize.width * image.scale,
+                              imagePixelSize.height * image.scale);
+  BOOL sameImageDimensions = CGSizeEqualToSize(referenceImagePixelSize, imagePixelSize);
   if (sameImageDimensions && [referenceImage fb_compareWithImage:image tolerance:tolerance]) {
     return YES;
   }
 
   if (NULL != errorPtr) {
     NSString *errorDescription = sameImageDimensions ? @"Images different" : @"Images different sizes";
     NSString *errorReason = sameImageDimensions ? [NSString stringWithFormat:@"image pixels differed by more than %.2f%% from the reference image", tolerance * 100]
-                                                : [NSString stringWithFormat:@"referenceImage:%@, image:%@", NSStringFromCGSize(referenceImage.size), NSStringFromCGSize(image.size)];
+                                                : [NSString stringWithFormat:@"referenceImage:%@, image:%@", NSStringFromCGSize(referenceImagePixelSize), NSStringFromCGSize(imagePixelSize)];
     FBSnapshotTestControllerErrorCode errorCode = sameImageDimensions ? FBSnapshotTestControllerErrorCodeImagesDifferent : FBSnapshotTestControllerErrorCodeImagesDifferentSizes;
 
     *errorPtr = [NSError errorWithDomain:FBSnapshotTestControllerErrorDomain
@@ -236,9 +243,10 @@ - (NSString *)_fileNameForSelector:(SEL)selector
   if (self.isDeviceAgnostic) {
     fileName = FBDeviceAgnosticNormalizedFileName(fileName);
   }
-
-  if ([[UIScreen mainScreen] scale] > 1) {
-    fileName = [fileName stringByAppendingFormat:@"@%.fx", [[UIScreen mainScreen] scale]];
+
+  CGFloat scale = (self.manualScale > 0 ? self.manualScale : [[UIScreen mainScreen] scale]);
+  if (1 < scale) {
+    fileName = [fileName stringByAppendingFormat:@"@%.fx", scale];
   }
   fileName = [fileName stringByAppendingPathExtension:@"png"];
   return fileName;
@@ -343,12 +351,12 @@ - (UIImage *)_imageForViewOrLayer:(id)viewOrLayer
 {
   if ([viewOrLayer isKindOfClass:[UIView class]]) {
     if (_usesDrawViewHierarchyInRect) {
-      return [UIImage fb_imageForView:viewOrLayer];
+      return [UIImage fb_imageForView:viewOrLayer scale:self.manualScale];
     } else {
-      return [UIImage fb_imageForViewLayer:viewOrLayer];
+      return [UIImage fb_imageForViewLayer:viewOrLayer scale:self.manualScale];
     }
   } else if ([viewOrLayer isKindOfClass:[CALayer class]]) {
-    return [UIImage fb_imageForLayer:viewOrLayer];
+    return [UIImage fb_imageForLayer:viewOrLayer scale:self.manualScale];
   } else {
     [NSException raise:@"Only UIView and CALayer classes can be snapshotted" format:@"%@", viewOrLayer];
   }