我已经能够调整在SO上找到的一些代码,从我的视图的“屏幕截图”中生成一个动画GIF,但结果是不可预测的. GIF帧有时是完整图像,全帧(“替换”模式,如GIMP标记它),其他时间只是前一层的“差异”(“组合”模式).
从我所看到的,当涉及更少和/或更小的帧时,CG将GIF写入“组合”模式,但未能使颜色正确.实际上,运动部件颜色正确,背景错误.
当CG将GIF保存为全帧时,颜色正常.文件大小更大,但是嘿,显然你不可能拥有两全其美. 🙂
有没有办法:
a) force CG to create "full frames" when saving the GIF
b) fix the colors (color table?)
我所做的是(ARC模式):
捕获视图的可见部分
[[scrollView contentView] dataWithPDFInsideRect:[[scrollView contentView] visibleRect]];
将其转换并调整为PNG类型的NSImageBitmapRep
-(NSMutableDictionary*) pngImageProps:(int)quality {
NSMutableDictionary *pngImageProps;
pngImageProps = [[NSMutableDictionary alloc] init];
[pngImageProps setValue:[NSNumber numberWithBool:NO] forKey:NSImageInterlaced];
double compressionF = 1;
[pngImageProps setValue:[NSNumber numberWithFloat:compressionF] forKey:NSImageCompressionFactor];
return pngImageProps;
}
-(NSData*) resizeImageToData:(NSData*)data toDimX:(int)xdim andDimY:(int)ydim withQuality:(int)quality{
NSImage *image = [[NSImage alloc] initWithData:data];
NSRect inRect = NSZeroRect;
inRect.size = [image size];
NSRect outRect = NSMakeRect(0, 0, xdim, ydim);
NSImage *outImage = [[NSImage alloc] initWithSize:outRect.size];
[outImage lockFocus];
[image drawInRect:outRect fromRect:inRect operation:NSCompositeCopy fraction:1];
NSBitmapImageRep* bitmapRep = [[NSBitmapImageRep alloc] initWithFocusedViewRect:outRect];
[outImage unlockFocus];
NSMutableDictionary *imageProps = [self pngImageProps:quality];
NSData* imageData = [bitmapRep representationUsingType:NSPNGFileType properties:imageProps];
return [imageData copy];
}
获取BitmapReps数组并创建GIF
-(CGImageRef) pngRepDataToCgImageRef:(NSData*)data {
CFDataRef imgData = (__bridge CFDataRef)data;
CGDataProviderRef imgDataProvider = CGDataProviderCreateWithCFData (imgData);
CGImageRef image = CGImageCreateWithPNGDataProvider(imgDataProvider, NULL, true, kCGRenderingIntentDefault);
return image;
}
////////// create GIF from
NSArray *images; // holds all BitmapReps
CGImageDestinationRef destination = CGImageDestinationCreateWithURL((__bridge CFURLRef)[NSURL fileURLWithPath:pot],
kUTTypeGIF,
allImages,
NULL);
// set frame delay
NSDictionary *frameProperties = [NSDictionary
dictionaryWithObject:[NSDictionary
dictionaryWithObject:[NSNumber numberWithFloat:0.2f]
forKey:(NSString *) kCGImagePropertyGIFDelayTime]
forKey:(NSString *) kCGImagePropertyGIFDictionary];
// set gif color properties
NSMutableDictionary *gifPropsDict = [[NSMutableDictionary alloc] init];
[gifPropsDict setObject:(NSString *)kCGImagePropertyColorModelRGB forKey:(NSString *)kCGImagePropertyColorModel];
[gifPropsDict setObject:[NSNumber numberWithBool:YES] forKey:(NSString *)kCGImagePropertyGIFHasGlobalColorMap];
// set gif loop
NSDictionary *gifProperties = [NSDictionary
dictionaryWithObject:gifPropsDict
forKey:(NSString *) kCGImagePropertyGIFDictionary];
// loop through frames and add them to GIF
for (int i=0; i < [images count]; i++) {
NSData *imageData = [images objectAtIndex:i];
CGImageRef imageRef = [self pngRepDataToCgImageRef:imageData];
CGImageDestinationAddImage(destination, imageRef, (__bridge CFDictionaryRef) (frameProperties));
}
// save the GIF
CGImageDestinationSetProperties(destination, (__bridge CFDictionaryRef)(gifProperties));
CGImageDestinationFinalize(destination);
CFRelease(destination);
我已经检查了ImageBitmapReps,当单独保存为PNG时,它们就可以了.
据我所知,颜色表应该由CG处理,还是我负责产生抖动的颜色?怎么做?
即使重复进行相同的动画,制作的GIF也可能会有所不同.
这是一个BitmapRep
single frame http://andraz.eu/stuff/gif/frame.png
这是带有无效颜色的GIF(“组合”模式)
combined frames http://andraz.eu/stuff/gif/anim2.gif
最佳答案 我读了你的代码.在创建CGImageDestinationRef和“[images count]”时,请仔细检查“allImages”.
以下测试代码工作正常:
NSDictionary *prep = [NSDictionary dictionaryWithObject:[NSDictionary dictionaryWithObject:[NSNumber numberWithFloat:0.2f] forKey:(NSString *) kCGImagePropertyGIFDelayTime] forKey:(NSString *) kCGImagePropertyGIFDictionary];
CGImageDestinationRef dst = CGImageDestinationCreateWithURL((__bridge CFURLRef)(fileURL), kUTTypeGIF, [filesArray count], nil);
for (int i=0;i<[filesArray count];i++)
{
//load anImage from array
...
CGImageRef imageRef=[anImage CGImageForProposedRect:nil context:nil hints:nil];
CGImageDestinationAddImage(dst, imageRef,(__bridge CFDictionaryRef)(prep));
}
bool fileSave = CGImageDestinationFinalize(dst);
CFRelease(dst);