Objective-C (ImageIO フレームワークを使用) を使用して GIF に変換している PNG がありますが、アルファ チャネルが奇妙に変換されています。
たとえば、正方形の上に光沢のある半透明のオーバーレイが付いた赤い正方形があり、ある種のベベルのように見えます。画像を PNG として保存してから、objective-c で GIF に変換しようとします。半透明の光沢が存在するセクション全体が変換されると、真っ白になります (または、UIView が UIImage の背後にある色)。
PNG画像の辞書の値を適切に設定していないと思います...では、可能な値は次のとおりです。
kCGImagePropertyPNGInterlaceType
また
kCGImagePropertyPNGsRGBIntent
これは、gifをアニメーションgifに変換してからクリップボードにコピーするためのコードです(これは機能しますが、一部のpngのアルファチャンネルが失われます)
NSString *path = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"animated.gif"];
CGImageDestinationRef destination = CGImageDestinationCreateWithURL((CFURLRef)[NSURL fileURLWithPath:path],
kUTTypeGIF,
16,
NULL);
NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithCapacity:5];
//[dict setObject:(NSString *) ??? forKey:(NSString *)kCGImagePropertyPNGInterlaceType];
//[dict setObject:(NSString *) ??? forKey:(NSString *)kCGImagePropertyPNGsRGBIntent];
NSDictionary *frameProperties = [ NSDictionary dictionaryWithObject: dict
forKey: (NSString*) kCGImagePropertyPNGDictionary ];
NSMutableDictionary *dict2 = [NSMutableDictionary dictionaryWithCapacity:5];
const uint8_t colorTable2[ 9 ] = { 0, 0, 0, 128, 128, 128, 255,255,255};
NSData* colorTableData2 = [ NSData dataWithBytes: colorTable2 length: 9 ];
[dict2 setObject:colorTableData2 forKey:(NSString *)kCGImagePropertyGIFImageColorMap];
[dict2 setObject:[NSNumber numberWithInt:0] forKey:(NSString *)kCGImagePropertyGIFLoopCount];
[dict2 setObject:[NSNumber numberWithFloat:0.005] forKey:(NSString *)kCGImagePropertyGIFDelayTime];
NSDictionary *gifProperties = [ NSDictionary dictionaryWithObject: dict2
forKey: (NSString*) kCGImagePropertyGIFDictionary ];
CGImageDestinationAddImage(destination, image1.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image2.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image3.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image4.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image5.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image6.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image7.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image8.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image9.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image10.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image11.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image12.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image13.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image14.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image15.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationAddImage(destination, image16.image.CGImage, (CFDictionaryRef)frameProperties);
CGImageDestinationSetProperties(destination, (CFDictionaryRef)gifProperties);
CGImageDestinationFinalize(destination);
CFRelease(destination);
NSData *gifData = [[NSData alloc] initWithContentsOfFile:path];
UIPasteboard *pasteboard = [UIPasteboard generalPasteboard];
[pasteboard setData:gifData forPasteboardType:@"com.compuserve.gif"];
[gifData release];