Behavior changes: change the default tint transformer to use `sourceIn` instead of `sourceAtop`

This matches the Apple UIKit's naming and behavior

SDWebImage/Core/SDImageTransformer.h

@@ -223,7 +223,7 @@ FOUNDATION_EXPORT NSString * _Nullable SDThumbnailedKeyForKey(NSString * _Nullab
  The tint color.
  */
 @property (nonatomic, strong, readonly, nonnull) UIColor *tintColor;
-/// The blend mode, defaults to `sourceAtop` if you use the old initializer
+/// The blend mode, defaults to `sourceIn` if you use the initializer without blend mode
 @property (nonatomic, assign, readonly) CGBlendMode blendMode;
 
 - (nonnull instancetype)init NS_UNAVAILABLE;

SDWebImage/Core/SDImageTransformer.m

@@ -252,7 +252,7 @@ NSString * _Nullable SDThumbnailedKeyForKey(NSString * _Nullable key, CGSize thu
 @implementation SDImageTintTransformer
 
 + (instancetype)transformerWithColor:(UIColor *)tintColor {
-    return [self transformerWithColor:tintColor blendMode:kCGBlendModeSourceAtop];
+    return [self transformerWithColor:tintColor blendMode:kCGBlendModeSourceIn];
 }
 
 + (instancetype)transformerWithColor:(UIColor *)tintColor blendMode:(CGBlendMode)blendMode {

SDWebImage/Core/UIImage+Transform.h

@@ -98,7 +98,8 @@ typedef NS_OPTIONS(NSUInteger, SDRectCorner) {
 #pragma mark - Image Blending
 
 /**
- Return a tinted image with the given color. This actually use `sourceAtop` blend mode.
+ Return a tinted image with the given color. This actually use `sourceIn` blend mode.
+ @note Before 5.20, this API actually use `sourceAtop` and cause naming confusing. After 5.20, we match UIKit's behavior using `sourceIn`.
  
  @param tintColor  The tint color.
  @return The new image with the tint color.
@@ -107,7 +108,7 @@ typedef NS_OPTIONS(NSUInteger, SDRectCorner) {
 
 /**
  Return a tinted image with the given color and blend mode.
- @note The blend mode treat `self` as background image (destination), treat `tintColor` as input image (source). So mostly you need `source` variant blend mode (use `sourceAtop` not `destinationAtop`).
+ @note The blend mode treat `self` as background image (destination), treat `tintColor` as input image (source). So mostly you need `source` variant blend mode (use `sourceIn` not `destinationIn`), which is different from UIKit's `+[UIImage imageWithTintColor:]`.
  
  @param tintColor  The tint color.
  @param blendMode The blend mode.

SDWebImage/Core/UIImage+Transform.m

@@ -627,7 +627,7 @@ static NSString * _Nullable SDGetCIFilterNameFromBlendMode(CGBlendMode blendMode
 }
 
 - (nullable UIImage *)sd_tintedImageWithColor:(nonnull UIColor *)tintColor {
-    return [self sd_tintedImageWithColor:tintColor blendMode:kCGBlendModeSourceAtop];
+    return [self sd_tintedImageWithColor:tintColor blendMode:kCGBlendModeSourceIn];
 }
 
 - (nullable UIImage *)sd_tintedImageWithColor:(nonnull UIColor *)tintColor blendMode:(CGBlendMode)blendMode {
@@ -694,7 +694,7 @@ static NSString * _Nullable SDGetCIFilterNameFromBlendMode(CGBlendMode blendMode
                 // MAX
                 ciImage = [ciImage imageByApplyingFilter:@"CIColorClamp" withInputParameters:nil];
             } else {
-                SD_LOG("UIImage+Transform error: Unsupported blend mode: %zu", blendMode);
+                SD_LOG("UIImage+Transform error: Unsupported blend mode: %d", blendMode);
                 ciImage = nil;
             }
         }

Tests/Tests/SDImageTransformerTests.m

@@ -244,9 +244,33 @@ static void SDAssertCGImageFirstComponentWhite(CGImageRef image, OSType pixelTyp
     expect([topCenterColor.sd_hexString isEqualToString:[UIColor blackColor].sd_hexString]).beTruthy();
     
     UIImage *tintedSourceInImage = [testImage sd_tintedImageWithColor:tintColor blendMode:kCGBlendModeSourceIn];
-    centerColor = [tintedSourceInImage sd_colorAtPoint:CGPointMake(150, 150)];
+    topCenterColor = [tintedSourceInImage sd_colorAtPoint:CGPointMake(150, 20)];
-    expect([centerColor.sd_hexString isEqualToString:[UIColor blackColor].sd_hexString]).beTruthy();
+#if SD_UIKIT
+    // Test UIKit's tint color behavior
+    if (@available(iOS 13.0, tvOS 13.0, watchOS 6.0, *)) {
+        UIImage *tintedSystemImage = [testImage imageWithTintColor:tintColor renderingMode:UIImageRenderingModeAlwaysTemplate];
+        UIGraphicsImageRendererFormat *format = UIGraphicsImageRendererFormat.preferredFormat;
+        format.scale = tintedSourceInImage.scale;
+        UIGraphicsImageRenderer *renderer = [[UIGraphicsImageRenderer alloc] initWithSize:tintedSystemImage.size format:format];
+        // Draw template image
+        tintedSystemImage = [renderer imageWithActions:^(UIGraphicsImageRendererContext * _Nonnull rendererContext) {
+                [tintedSystemImage drawInRect:CGRectMake(0, 0, tintedSystemImage.size.width, tintedSystemImage.size.height)];
+        }];
+        UIColor *testColor1 = [tintedSourceInImage sd_colorAtPoint:CGPointMake(150, 20)];
+        UIColor *testColor2 = [tintedSystemImage sd_colorAtPoint:CGPointMake(150, 20)];
+        CGFloat r1, g1, b1, a1;
+        CGFloat r2, g2, b2, a2;
+        [testColor1 getRed:&r1 green:&g1 blue:&b1 alpha:&a1];
+        [testColor2 getRed:&r2 green:&g2 blue:&b2 alpha:&a2];
+        expect(r1).beCloseToWithin(r2, 0.01);
+        expect(g1).beCloseToWithin(g2, 0.01);
+        expect(b1).beCloseToWithin(b2, 0.01);
+        expect(a1).beCloseToWithin(a2, 0.01);
     }
+#endif
+    expect([topCenterColor.sd_hexString isEqualToString:tintColor.sd_hexString]).beTruthy();
+}
+#pragma clang diagnostic pop
 
 - (void)test07UIImageTransformBlurCG {
     [self test07UIImageTransformBlurWithImage:self.testImageCG];
@@ -357,7 +381,7 @@ static void SDAssertCGImageFirstComponentWhite(CGImageRef image, OSType pixelTyp
                       @"SDImageRoundCornerTransformer(50.000000,18446744073709551615,1.000000,#ff000000)",
                       @"SDImageFlippingTransformer(1,1)",
                       @"SDImageCroppingTransformer({0.000000,0.000000,50.000000,50.000000})",
-                      @"SDImageTintTransformer(#00000000,20)",
+                      @"SDImageTintTransformer(#00000000,18)",
                       @"SDImageBlurTransformer(5.000000)",
                       @"SDImageFilterTransformer(CIColorInvert)"
                       ];