Tests/Tests/SDImageCacheTests.m (2)

506-522: ⚠️ Potential issue | 🟡 Minor

Stale test description and comment.

Line 441 (expectation5's description) still says "should use GIF", and Line 506's comment says "should use GIF not APNG". Both are now inaccurate since newer OS versions will expect PNG. Update them to reflect the version-dependent behavior.

📝 Suggested updates

-    XCTestExpectation *expectation5 = [self expectationWithDescription:@"StoreImage UIAnimatedImage without sd_imageFormat should use GIF"];
+    XCTestExpectation *expectation5 = [self expectationWithDescription:@"StoreImage UIAnimatedImage without sd_imageFormat should use APNG on iOS 12+/GIF otherwise"];

-    // Case 5: UIAnimatedImage without sd_imageFormat should use GIF not APNG
+    // Case 5: UIAnimatedImage without sd_imageFormat should use APNG on newer OS, GIF on older OS

---

514-517: ⚠️ Potential issue | 🟡 Minor

Stale inline comment on Line 516.

The comment // Should save to GIF is no longer accurate — on newer OS versions it saves to PNG/APNG.

SDWebImage/Core/SDImageCoderHelper.m (1)

178-197: ⚠️ Potential issue | 🔴 Critical

Bug: format variable is declared but never used — animated frames always encoded as GIF.

Lines 178–183 compute format based on OS version (PNG for iOS 12+ / macOS 10.14+, GIF otherwise), but line 184 ignores it and hardcodes SDImageFormatGIF:

CFStringRef imageUTType = [NSData sd_UTTypeFromImageFormat:SDImageFormatGIF]; // always GIF

Additionally, line 196 uses GIF-specific property keys (kCGImagePropertyGIFDictionary / kCGImagePropertyGIFDelayTime) regardless of the format. For APNG, these should use the PNG-specific equivalents nested inside kCGImagePropertyPNGDictionary (e.g., kCGImagePropertyAPNGDelayTime).

As a result, animatedImageWithFrames: always produces GIF data regardless of OS version, defeating the purpose of this PR.

🐛 Proposed fix

     SDImageFormat format;
     if (`@available`(iOS 12.0, tvOS 12.0, macOS 10.14, watchOS 5.0, *)) {
         format = SDImageFormatPNG;
     } else {
         format = SDImageFormatGIF;
     }
-    CFStringRef imageUTType = [NSData sd_UTTypeFromImageFormat:SDImageFormatGIF];
-    // Create an image destination. GIF does not support EXIF image orientation
+    CFStringRef imageUTType = [NSData sd_UTTypeFromImageFormat:format];
+    // Create an image destination. GIF/APNG does not support EXIF image orientation
     CGImageDestinationRef imageDestination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)imageData, imageUTType, frameCount, NULL);
     if (!imageDestination) {
         // Handle failure.
         return nil;
     }
     
     for (size_t i = 0; i < frameCount; i++) {
         SDImageFrame *frame = frames[i];
         NSTimeInterval frameDuration = frame.duration;
         CGImageRef frameImageRef = frame.image.CGImage;
-        NSDictionary *frameProperties = @{(__bridge NSString *)kCGImagePropertyGIFDictionary : @{(__bridge NSString *)kCGImagePropertyGIFDelayTime : @(frameDuration)}};
+        NSDictionary *frameProperties;
+        if (format == SDImageFormatPNG) {
+            frameProperties = @{(__bridge NSString *)kCGImagePropertyPNGDictionary : @{(__bridge NSString *)kCGImagePropertyAPNGDelayTime : @(frameDuration)}};
+        } else {
+            frameProperties = @{(__bridge NSString *)kCGImagePropertyGIFDictionary : @{(__bridge NSString *)kCGImagePropertyGIFDelayTime : @(frameDuration)}};
+        }
         CGImageDestinationAddImage(imageDestination, frameImageRef, (__bridge CFDictionaryRef)frameProperties);
     }