压缩图片，重新绘制图片，得到没有透明度的图片
- (nullable UIImage *)sd_decompressedImageWithImage:(nullable UIImage *)image {
if (![[self class] shouldDecodeImage:image]) {//是否可以解码图片
return image;
}
// autorelease the bitmap context and all vars to help system to free memory when there are memory warning.
// on iOS7, do not forget to call [[SDImageCache sharedImageCache] clearMemory];
@autoreleasepool{
CGImageRef imageRef = image.CGImage;
CGColorSpaceRef colorspaceRef = [[self class] colorSpaceForImageRef:imageRef];//获取色彩空间
size_t width = CGImageGetWidth(imageRef);
size_t height = CGImageGetHeight(imageRef);
// kCGImageAlphaNone is not supported in CGBitmapContextCreate.
// Since the original image here has no alpha info, use kCGImageAlphaNoneSkipLast
// to create bitmap graphics contexts without alpha info.
//重新绘制图片，得到没有透明度的图片
CGContextRef context = CGBitmapContextCreate(NULL,
width,
height,
kBitsPerComponent,
0,
colorspaceRef,
kCGBitmapByteOrderDefault|kCGImageAlphaNoneSkipLast);
if (context == NULL) {
return image;
}
// Draw the image into the context and retrieve the new bitmap image without alpha
CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
CGImageRef imageRefWithoutAlpha = CGBitmapContextCreateImage(context);
UIImage *imageWithoutAlpha = [UIImage imageWithCGImage:imageRefWithoutAlpha
scale:image.scale
orientation:image.imageOrientation];
CGContextRelease(context);
CGImageRelease(imageRefWithoutAlpha);
return imageWithoutAlpha;
}
}
压缩图片并且缩小图片尺寸，这个方法比较长，我已经在里面把必要的标注标出来了
- (nullable UIImage *)sd_decompressedAndScaledDownImageWithImage:(nullable UIImage *)image {
if (![[self class] shouldDecodeImage:image]) {//是否可以解码图片
return image;
}
if (![[self class] shouldScaleDownImage:image]) {//是否可以缩小图片
return [self sd_decompressedImageWithImage:image];
}
CGContextRef destContext;
// autorelease the bitmap context and all vars to help system to free memory when there are memory warning.
// on iOS7, do not forget to call [[SDImageCache sharedImageCache] clearMemory];
@autoreleasepool {
CGImageRef sourceImageRef = image.CGImage; //拿到图片属性
CGSize sourceResolution = CGSizeZero; //拿到图片的宽和高
sourceResolution.width = CGImageGetWidth(sourceImageRef);
sourceResolution.height = CGImageGetHeight(sourceImageRef);
float sourceTotalPixels = sourceResolution.width * sourceResolution.height;//原图总像素
// Determine the scale ratio to apply to the input image
// that results in an output image of the defined size.
// see kDestImageSizeMB, and how it relates to destTotalPixels.
float imageScale = kDestTotalPixels / sourceTotalPixels; //计算压缩比例
CGSize destResolution = CGSizeZero; //目标像素
destResolution.width = (int)(sourceResolution.width*imageScale);////目标像素宽
destResolution.height = (int)(sourceResolution.height*imageScale);////目标像素高
// current color space
CGColorSpaceRef colorspaceRef = [[self class] colorSpaceForImageRef:sourceImageRef];//颜色空间
// kCGImageAlphaNone is not supported in CGBitmapContextCreate.
// Since the original image here has no alpha info, use kCGImageAlphaNoneSkipLast
// to create bitmap graphics contexts without alpha info.
destContext = CGBitmapContextCreate(NULL,
destResolution.width,
destResolution.height,
kBitsPerComponent,
0,
colorspaceRef,
kCGBitmapByteOrderDefault|kCGImageAlphaNoneSkipLast);
if (destContext == NULL) {
return image;
}
CGContextSetInterpolationQuality(destContext, kCGInterpolationHigh); //设置压缩质量
// Now define the size of the rectangle to be used for the
// incremental blits from the input image to the output image.
// we use a source tile width equal to the width of the source
// image due to the way that iOS retrieves image data from disk.
// iOS must decode an image from disk in full width 'bands', even
// if current graphics context is clipped to a subrect within that
// band. Therefore we fully utilize all of the pixel data that results
// from a decoding opertion by achnoring our tile size to the full
// width of the input image.
//计算第一个原图方块 sourceTile，这个方块的宽度同原图一样，高度根据方块容量计算
CGRect sourceTile = CGRectZero;
sourceTile.size.width = sourceResolution.width;
// The source tile height is dynamic. Since we specified the size
// of the source tile in MB, see how many rows of pixels high it
// can be given the input image width.
sourceTile.size.height = (int)(kTileTotalPixels / sourceTile.size.width );
sourceTile.origin.x = 0.0f;
// The output tile is the same proportions as the input tile, but
// scaled to image scale.
CGRect destTile;//计算目标图像方块 destTile
destTile.size.width = destResolution.width;
destTile.size.height = sourceTile.size.height * imageScale;
destTile.origin.x = 0.0f;
// The source seem overlap is proportionate to the destination seem overlap.
// this is the amount of pixels to overlap each tile as we assemble the ouput image.
//计算原图像方块与方块重叠的像素大小 sourceSeemOverlap
float sourceSeemOverlap = (int)((kDestSeemOverlap/destResolution.height)*sourceResolution.height);
CGImageRef sourceTileImageRef;
// calculate the number of read/write operations required to assemble the
// output image.
//计算原图像需要被分割成多少个方块 iterations
int iterations = (int)( sourceResolution.height / sourceTile.size.height );
// If tile height doesn't divide the image height evenly, add another iteration
// to account for the remaining pixels.
int remainder = (int)sourceResolution.height % (int)sourceTile.size.height;
if(remainder) {
iterations++;
}
// Add seem overlaps to the tiles, but save the original tile height for y coordinate calculations.
//根据重叠像素计算原图方块的大小后，获取原图中该方块内的数据，把该数据写入到相对应的目标方块中
float sourceTileHeightMinusOverlap = sourceTile.size.height;
sourceTile.size.height += sourceSeemOverlap;
destTile.size.height += kDestSeemOverlap;
for( int y = 0; y < iterations; ++y ) {
@autoreleasepool {
sourceTile.origin.y = y * sourceTileHeightMinusOverlap + sourceSeemOverlap;
destTile.origin.y = destResolution.height - (( y + 1 ) * sourceTileHeightMinusOverlap * imageScale + kDestSeemOverlap);
sourceTileImageRef = CGImageCreateWithImageInRect( sourceImageRef, sourceTile );
if( y == iterations - 1 && remainder ) {
float dify = destTile.size.height;
destTile.size.height = CGImageGetHeight( sourceTileImageRef ) * imageScale;
dify -= destTile.size.height;
destTile.origin.y += dify;
}
CGContextDrawImage( destContext, destTile, sourceTileImageRef );
CGImageRelease( sourceTileImageRef );
}
}
//返回目标图像
CGImageRef destImageRef = CGBitmapContextCreateImage(destContext);
CGContextRelease(destContext);
if (destImageRef == NULL) {
return image;
}
UIImage *destImage = [UIImage imageWithCGImage:destImageRef scale:image.scale orientation:image.imageOrientation];
CGImageRelease(destImageRef);
if (destImage == nil) {
return image;
}
return destImage;
}
}
确定是否可以编码,webP不支持，HEIC通过canEncodeToHEICFormat方法来判断，其他的类型可以
- (BOOL)canEncodeToFormat:(SDImageFormat)format {
switch (format) {
case SDImageFormatWebP:
// Do not support WebP encoding
return NO;
case SDImageFormatHEIC:
// Check HEIC encoding compatibility
return [[self class] canEncodeToHEICFormat];
default:
return YES;
}
}
编码
- (NSData *)encodedDataWithImage:(UIImage *)image format:(SDImageFormat)format {
if (!image) {
return nil;
}
if (format == SDImageFormatUndefined) { //若没有指定类型，如果有透明度，就是png，没有就是jpeg
BOOL hasAlpha = SDCGImageRefContainsAlpha(image.CGImage);
if (hasAlpha) {
format = SDImageFormatPNG;
} else {
format = SDImageFormatJPEG;
}
}
NSMutableData *imageData = [NSMutableData data];
CFStringRef imageUTType = [NSData sd_UTTypeFromSDImageFormat:format];//转换成系统的图片类型
// Create an image destination.
CGImageDestinationRef imageDestination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)imageData, imageUTType, 1, NULL);//创建一个Image Destination
if (!imageDestination) {
// Handle failure.
return nil;
}
NSMutableDictionary *properties = [NSMutableDictionary dictionary];
#if SD_UIKIT || SD_WATCH
NSInteger exifOrientation = [SDWebImageCoderHelper exifOrientationFromImageOrientation:image.imageOrientation];
[properties setValue:@(exifOrientation) forKey:(__bridge_transfer NSString *)kCGImagePropertyOrientation];
#endif
// Add your image to the destination. 添加数据和图片
CGImageDestinationAddImage(imageDestination, image.CGImage, (__bridge CFDictionaryRef)properties);
// Finalize the destination. 最后调用，完成数据写入
if (CGImageDestinationFinalize(imageDestination) == NO) {
// Handle failure.
imageData = nil;
}
CFRelease(imageDestination);
return [imageData copy];
}
首先需要创建一个Image Destination，可以通过三种方式CGImageDestinationCreateWithURL, CGImageDestinationCreateWithData, or CGImageDestinationCreateWithDataConsumer（目前不知道URL路径怎么设置才能存入...orz）
- (void) writeCGImage: (CGImageRef) image toURL: (NSURL*) url withType: (CFStringRef) imageType andOptions: (CFDictionaryRef) options
{
CGImageDestinationRef myImageDest = CGImageDestinationCreateWithURL((CFURLRef)url, imageType, 1, nil);
CGImageDestinationAddImage(myImageDest, image, options);//添加数据和图片
CGImageDestinationFinalize(myImageDest);//最后调用，完成数据写入
CFRelease(myImageDest);
}
是否可以解码image，若有透明度，则不需要解码
+ (BOOL)shouldDecodeImage:(nullable UIImage *)image {
// Prevent "CGBitmapContextCreateImage: invalid context 0x0" error
if (image == nil) {
return NO;
}
// do not decode animated images
if (image.images != nil) {
return NO;
}
CGImageRef imageRef = image.CGImage;
BOOL hasAlpha = SDCGImageRefContainsAlpha(imageRef);
// do not decode images with alpha
if (hasAlpha) {
return NO;
}
return YES;
}
是否支持HEIC类型的解码 ，iOS 11+ 的设备可以解码，其他的不可以
+ (BOOL)canDecodeFromHEICFormat {
static BOOL canDecode = NO;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
#if TARGET_OS_SIMULATOR || SD_WATCH
canDecode = NO;
#elif SD_MAC
NSProcessInfo *processInfo = [NSProcessInfo processInfo];
if ([processInfo respondsToSelector:@selector(operatingSystemVersion)]) {
// macOS 10.13+
canDecode = processInfo.operatingSystemVersion.minorVersion >= 13;
} else {
canDecode = NO;
}
#elif SD_UIKIT
NSProcessInfo *processInfo = [NSProcessInfo processInfo];
if ([processInfo respondsToSelector:@selector(operatingSystemVersion)]) {
// iOS 11+ && tvOS 11+
canDecode = processInfo.operatingSystemVersion.majorVersion >= 11;
} else {
canDecode = NO;
}
#endif
});
return canDecode;
}
是否可以进行HEIC编码，通过判断HEIC是否可以写入imageDestination来确定是否可以编码
+ (BOOL)canEncodeToHEICFormat {
static BOOL canEncode = NO;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
NSMutableData *imageData = [NSMutableData data];
CFStringRef imageUTType = [NSData sd_UTTypeFromSDImageFormat:SDImageFormatHEIC];
// Create an image destination.
CGImageDestinationRef imageDestination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)imageData, imageUTType, 1, NULL);
if (!imageDestination) {
// Can't encode to HEIC
canEncode = NO;
} else {
// Can encode to HEIC
CFRelease(imageDestination);
canEncode = YES;
}
});
return canEncode;
}
转向标签转换器
+ (UIImageOrientation)sd_imageOrientationFromImageData:(nonnull NSData *)imageData {
UIImageOrientation result = UIImageOrientationUp;
CGImageSourceRef imageSource = CGImageSourceCreateWithData((__bridge CFDataRef)imageData, NULL);
if (imageSource) {
CFDictionaryRef properties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, NULL);
if (properties) {
CFTypeRef val;
NSInteger exifOrientation;
val = CFDictionaryGetValue(properties, kCGImagePropertyOrientation);
if (val) {
CFNumberGetValue(val, kCFNumberNSIntegerType, &exifOrientation);
result = [SDWebImageCoderHelper imageOrientationFromEXIFOrientation:exifOrientation];
} // else - if it's not set it remains at up
CFRelease((CFTypeRef) properties);
} else {
//NSLog(@"NO PROPERTIES, FAIL");
}
CFRelease(imageSource);
}
return result;
}
是否可以剪切image，若有透明度，则不需要剪切
+ (BOOL)shouldScaleDownImage:(nonnull UIImage *)image {
BOOL shouldScaleDown = YES;
CGImageRef sourceImageRef = image.CGImage;
CGSize sourceResolution = CGSizeZero;
sourceResolution.width = CGImageGetWidth(sourceImageRef);
sourceResolution.height = CGImageGetHeight(sourceImageRef);
float sourceTotalPixels = sourceResolution.width * sourceResolution.height;
float imageScale = kDestTotalPixels / sourceTotalPixels;
if (imageScale < 1) {
shouldScaleDown = YES;
} else {
shouldScaleDown = NO;
}
return shouldScaleDown;
}
获取色彩空间
+ (CGColorSpaceRef)colorSpaceForImageRef:(CGImageRef)imageRef {
// current
CGColorSpaceModel imageColorSpaceModel = CGColorSpaceGetModel(CGImageGetColorSpace(imageRef));//获取CGColorSpaceModel信息
CGColorSpaceRef colorspaceRef = CGImageGetColorSpace(imageRef);
BOOL unsupportedColorSpace = (imageColorSpaceModel == kCGColorSpaceModelUnknown ||
imageColorSpaceModel == kCGColorSpaceModelMonochrome ||
imageColorSpaceModel == kCGColorSpaceModelCMYK ||
imageColorSpaceModel == kCGColorSpaceModelIndexed);
if (unsupportedColorSpace) {
colorspaceRef = SDCGColorSpaceGetDeviceRGB(); //若不支持色彩空间 ，则默认去图像的 RGBA 色彩 （显示3色）
}
return colorspaceRef;
}
获取色彩空间扩展：
通用标准创建
// 灰度 色彩
CGColorSpaceRef graySpaceRef = CGColorSpaceCreateDeviceGray();
// RGBA 色彩 （显示3色）
CGColorSpaceRef rgbSapceRef = CGColorSpaceCreateDeviceRGB();
// CMYK 色彩 （印刷4色）
CGColorSpaceRef cmykSpaceRef = CGColorSpaceCreateDeviceCMYK();
色彩校正
// 灰度 色彩矫正
// CGFloat whitePoint[] = {0, 100, 200};// CIE XYZ 值
// CGFloat blackPoint[] = {200, 100, 0};
// CGFloat calibratedGrayComponents[] = {0.6, 0.6};
// CGColorSpaceRef calibratedGraySpaceRef = CGColorSpaceCreateCalibratedGray(whitePoint, blackPoint, 0.5);
// CGColorRef calibratedGrayColorRef = CGColorCreate(calibratedGraySpaceRef, calibratedGrayComponents);
// RGB 色彩矫正 （数据不太对，见谅，水好深）
// CGFloat whitePoint[] = {0, 100, 200};// CIE XYZ 值
// CGFloat blackPoint[] = {200, 100, 0};
// CGFloat gamma[] = {0, 0, 0};
// CGFloat matrix[] = {0, 100, 200, 0, 100, 200, 0, 100, 200};
// CGFloat calibratedRGBComponents[] = {1, 0, 0, 1};
// CGColorSpaceRef calibratedRGBSpaceRef = CGColorSpaceCreateCalibratedRGB(whitePoint, blackPoint, gamma, matrix);
// CGColorRef calibratedRGBColorRef = CGColorCreate(calibratedRGBSpaceRef, calibratedRGBComponents);
CGColorSpaceRef nameSpaceColor = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
// 根据名称创建
CG_EXTERN const CFStringRef kCGColorSpaceGenericGray
CG_AVAILABLE_STARTING(__MAC_10_4, __IPHONE_9_0);
CG_EXTERN const CFStringRef kCGColorSpaceGenericRGB
CG_AVAILABLE_STARTING(__MAC_10_4, __IPHONE_9_0);
CG_EXTERN const CFStringRef kCGColorSpaceGenericCMYK
CG_AVAILABLE_STARTING(__MAC_10_4, __IPHONE_9_0);
CG_EXTERN const CFStringRef kCGColorSpaceDisplayP3
CG_AVAILABLE_STARTING(__MAC_10_10, __IPHONE_9_0);
CG_EXTERN const CFStringRef kCGColorSpaceGenericRGBLinear
CG_AVAILABLE_STARTING(__MAC_10_5, __IPHONE_9_0);
CG_EXTERN const CFStringRef kCGColorSpaceAdobeRGB1998
CG_AVAILABLE_STARTING(__MAC_10_5, __IPHONE_9_0);
CG_EXTERN const CFStringRef kCGColorSpaceSRGB
CG_AVAILABLE_STARTING(__MAC_10_5, __IPHONE_9_0);
CG_EXTERN const CFStringRef kCGColorSpaceGenericGrayGamma2_2
CG_AVAILABLE_STARTING(__MAC_10_6, __IPHONE_9_0);
CG_EXTERN const CFStringRef kCGColorSpaceGenericXYZ
CG_AVAILABLE_STARTING(__MAC_10_11, __IPHONE_9_0);
CG_EXTERN const CFStringRef kCGColorSpaceACESCGLinear
CG_AVAILABLE_STARTING(__MAC_10_11, __IPHONE_9_0);
CG_EXTERN const CFStringRef kCGColorSpaceITUR_709
CG_AVAILABLE_STARTING(__MAC_10_11, __IPHONE_9_0);
CG_EXTERN const CFStringRef kCGColorSpaceITUR_2020
CG_AVAILABLE_STARTING(__MAC_10_11, __IPHONE_9_0);
CG_EXTERN const CFStringRef kCGColorSpaceROMMRGB
CG_AVAILABLE_STARTING(__MAC_10_11, __IPHONE_9_0);
CG_EXTERN const CFStringRef kCGColorSpaceDCIP3
CG_AVAILABLE_STARTING(__MAC_10_11, __IPHONE_9_0);
获取信息
CG_EXTERN CFTypeID CGColorSpaceGetTypeID(void)
CG_AVAILABLE_STARTING(__MAC_10_2, __IPHONE_2_0);
CG_EXTERN size_t CGColorSpaceGetNumberOfComponents(CGColorSpaceRef __nullable space)
CG_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);
CG_EXTERN CGColorSpaceModel CGColorSpaceGetModel(CGColorSpaceRef __nullable space)
CG_AVAILABLE_STARTING(__MAC_10_5, __IPHONE_2_0);
CG_EXTERN CGColorSpaceRef __nullable CGColorSpaceGetBaseColorSpace(CGColorSpaceRef __nullable space)
CG_AVAILABLE_STARTING(__MAC_10_5, __IPHONE_2_0);
CG_EXTERN size_t CGColorSpaceGetColorTableCount(CGColorSpaceRef __nullable space)
CG_AVAILABLE_STARTING(__MAC_10_5, __IPHONE_2_0);
CG_EXTERN void CGColorSpaceGetColorTable(CGColorSpaceRef __nullable space,
uint8_t * __nullable table) CG_AVAILABLE_STARTING(__MAC_10_5, __IPHONE_2_0);
CG_EXTERN CFDataRef __nullable CGColorSpaceCopyICCProfile(CGColorSpaceRef __nullable space)
CG_AVAILABLE_STARTING(__MAC_10_5, __IPHONE_6_0);
五、SDWebImageGIFCoder
是否可以解码，判断是否是GIF类型
- (BOOL)canDecodeFromData:(nullable NSData *)data {
return ([NSData sd_imageFormatForImageData:data] == SDImageFormatGIF);
}
//解码
import <ImageIO/ImageIO.h>
@interface CGImageGIFView ()
{
//gif的字典属性，定义了gif的一些特殊内容，这里虽然设置了，但是没啥特殊设置，一般情况下可以设置为NULL
NSDictionary *gifProperties;
size_t index;
size_t count;
CGImageSourceRef gifRef;
NSTimer *timer;
}
获取CGImageSourceGetCount，如果count <= 1 ,说明GIF图片张数最多是一张，直接返回就可以。
如果大于1张，通过for循环遍历每一张图片，获取图片和duration时间间隔，scale，方向设置为UIImageOrientationUp，然后合成一张新的图片，返回
- (UIImage *)decodedImageWithData:(NSData *)data {
if (!data) {
return nil;
}
#if SD_MAC
return [[UIImage alloc] initWithData:data];
#else
CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);
if (!source) {
return nil;
}
size_t count = CGImageSourceGetCount(source);//这个拿到的是图片的张数，一张gif其实内部是有好几张图片组合在一起的，如果是普通图片的话，拿到的数就等于1
UIImage *animatedImage;
if (count <= 1) {
animatedImage = [[UIImage alloc] initWithData:data];
} else {
NSMutableArray<SDWebImageFrame *> *frames = [NSMutableArray array];
for (size_t i = 0; i < count; i++) {
CGImageRef imageRef = CGImageSourceCreateImageAtIndex(source, i, NULL); //获取头像
if (!imageRef) {
continue;
}
float duration = [self sd_frameDurationAtIndex:i source:source];
#if SD_WATCH
CGFloat scale = 1;
scale = [WKInterfaceDevice currentDevice].screenScale;
#elif SD_UIKIT
CGFloat scale = 1;
scale = [UIScreen mainScreen].scale;
#endif
UIImage *image = [UIImage imageWithCGImage:imageRef scale:scale orientation:UIImageOrientationUp];
CGImageRelease(imageRef);
SDWebImageFrame *frame = [SDWebImageFrame frameWithImage:image duration:duration];
[frames addObject:frame];
}
NSUInteger loopCount = 1;
NSDictionary *imageProperties = (__bridge_transfer NSDictionary *)CGImageSourceCopyProperties(source, nil);//获取image属性
NSDictionary *gifProperties = [imageProperties valueForKey:(__bridge_transfer NSString *)kCGImagePropertyGIFDictionary];//设置gif的属性来获取gif的图片信息
if (gifProperties) {
NSNumber *gifLoopCount = [gifProperties valueForKey:(__bridge_transfer NSString *)kCGImagePropertyGIFLoopCount];//读取循环次数
if (gifLoopCount != nil) {
loopCount = gifLoopCount.unsignedIntegerValue;
}
}
animatedImage = [SDWebImageCoderHelper animatedImageWithFrames:frames];
animatedImage.sd_imageLoopCount = loopCount;
}
CFRelease(source);
return animatedImage;
#endif
}
获取间隔时间
- (float)sd_frameDurationAtIndex:(NSUInteger)index source:(CGImageSourceRef)source {
float frameDuration = 0.1f;//默认是0.1s
CFDictionaryRef cfFrameProperties = CGImageSourceCopyPropertiesAtIndex(source, index, nil);
NSDictionary *frameProperties = (__bridge NSDictionary *)cfFrameProperties;
NSDictionary *gifProperties = frameProperties[(NSString *)kCGImagePropertyGIFDictionary];
NSNumber *delayTimeUnclampedProp = gifProperties[(NSString *)kCGImagePropertyGIFUnclampedDelayTime];
if (delayTimeUnclampedProp != nil) {
frameDuration = [delayTimeUnclampedProp floatValue];
} else {
NSNumber *delayTimeProp = gifProperties[(NSString *)kCGImagePropertyGIFDelayTime];
if (delayTimeProp != nil) {
frameDuration = [delayTimeProp floatValue];
}
}
// Many annoying ads specify a 0 duration to make an image flash as quickly as possible.
// We follow Firefox's behavior and use a duration of 100 ms for any frames that specify
// a duration of <= 10 ms. See <rdar://problem/7689300> and <http://webkit.org/b/36082>
// for more information.
if (frameDuration < 0.011f) {
frameDuration = 0.100f;
}
CFRelease(cfFrameProperties);
return frameDuration;
}
压缩图像，gif图像不能压缩
- (UIImage *)decompressedImageWithImage:(UIImage *)image
data:(NSData *__autoreleasing _Nullable *)data
options:(nullable NSDictionary<NSString*, NSObject*>*)optionsDict {
// GIF do not decompress
return image;
}
是否可以编码，判断是否gif类型
- (BOOL)canEncodeToFormat:(SDImageFormat)format {
return (format == SDImageFormatGIF);
}
编码gif图像
- (NSData *)encodedDataWithImage:(UIImage *)image format:(SDImageFormat)format {
if (!image) {
return nil;
}
if (format != SDImageFormatGIF) {
return nil;
}
NSMutableData *imageData = [NSMutableData data];
CFStringRef imageUTType = [NSData sd_UTTypeFromSDImageFormat:SDImageFormatGIF];
NSArray<SDWebImageFrame *> *frames = [SDWebImageCoderHelper framesFromAnimatedImage:image];
// Create an image destination. GIF does not support EXIF image orientation
CGImageDestinationRef imageDestination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)imageData, imageUTType, frames.count, NULL);
if (!imageDestination) {
// Handle failure.
return nil;
}
if (frames.count == 0) {
// for static single GIF images
CGImageDestinationAddImage(imageDestination, image.CGImage, nil);
} else {
// for animated GIF images
NSUInteger loopCount = image.sd_imageLoopCount;
NSDictionary *gifProperties = @{(__bridge_transfer NSString *)kCGImagePropertyGIFDictionary: @{(__bridge_transfer NSString *)kCGImagePropertyGIFLoopCount : @(loopCount)}};
CGImageDestinationSetProperties(imageDestination, (__bridge CFDictionaryRef)gifProperties);
for (size_t i = 0; i < frames.count; i++) {
SDWebImageFrame *frame = frames[i];
float frameDuration = frame.duration;
CGImageRef frameImageRef = frame.image.CGImage;
NSDictionary *frameProperties = @{(__bridge_transfer NSString *)kCGImagePropertyGIFDictionary : @{(__bridge_transfer NSString *)kCGImagePropertyGIFUnclampedDelayTime : @(frameDuration)}};
CGImageDestinationAddImage(imageDestination, frameImageRef, (__bridge CFDictionaryRef)frameProperties);
}
}
// Finalize the destination.
if (CGImageDestinationFinalize(imageDestination) == NO) {
// Handle failure.
imageData = nil;
}
CFRelease(imageDestination);
return [imageData copy];
}
六、SDWebImageCoderHelper和SDWebImageFrame
SDWebImageCoderHelper.h
/**
Return an animated image with frames array.
For UIKit, this will apply the patch and then create animated UIImage. The patch is because that `+[UIImage animatedImageWithImages:duration:]` just use the averate of duration for each image. So it will not work if different frame has different duration. Therefore we repeat the specify frame for specify times to let it work.
For AppKit, NSImage does not support animates other than GIF. This will try to encode the frames to GIF format and then create an animated NSImage for rendering.
@param frames The frames array. If no frames or frames is empty, return nil
@return A animated image for rendering on UIImageView(UIKit) or NSImageView(AppKit)
帧数组返回动画图像,我们重复指定时间的指定框架让它工作。
对于它，NSImage并不支持GIF动画以外。这将尝试编码帧gif格式然后渲染创建一个动画nsimage。
*/
+ (UIImage * _Nullable)animatedImageWithFrames:(NSArray<SDWebImageFrame *> * _Nullable)frames;
/**
Return frames array from an animated image.
For UIKit, this will unapply the patch for the description above and then create frames array. This will also work for normal animated UIImage.
For AppKit, NSImage does not support animates other than GIF. This will try to decode the GIF imageRep and then create frames array.
@param animatedImage A animated image. If it's not animated, return nil
@return The frames array
返回一个frames array，gif图片转换成一个帧数组
*/
+ (NSArray<SDWebImageFrame *> * _Nullable)framesFromAnimatedImage:(UIImage * _Nullable)animatedImage;
#if SD_UIKIT || SD_WATCH
/**
Convert an EXIF image orientation to an iOS one.
@param exifOrientation EXIF orientation
@return iOS orientation
转换方向信息，有数字转换成type
*/
+ (UIImageOrientation)imageOrientationFromEXIFOrientation:(NSInteger)exifOrientation;
/**
Convert an iOS orientation to an EXIF image orientation.
@param imageOrientation iOS orientation
@return EXIF orientation
转换方向信息，有type转换成数字
*/
+ (NSInteger)exifOrientationFromImageOrientation:(UIImageOrientation)imageOrientation;
#endif
SDWebImageCoderHelper.m
将gif用帧动画的形式渲染到image上
+ (UIImage *)animatedImageWithFrames:(NSArray<SDWebImageFrame *> *)frames {
NSUInteger frameCount = frames.count;
if (frameCount == 0) {
return nil;
}
UIImage *animatedImage;
#if SD_UIKIT || SD_WATCH
NSUInteger durations[frameCount];
for (size_t i = 0; i < frameCount; i++) {
durations[i] = frames[i].duration * 1000;
}
NSUInteger const gcd = gcdArray(frameCount, durations);
__block NSUInteger totalDuration = 0;
NSMutableArray<UIImage *> *animatedImages = [NSMutableArray arrayWithCapacity:frameCount];
[frames enumerateObjectsUsingBlock:^(SDWebImageFrame * _Nonnull frame, NSUInteger idx, BOOL * _Nonnull stop) {
UIImage *image = frame.image;
NSUInteger duration = frame.duration * 1000;
totalDuration += duration;
NSUInteger repeatCount;
if (gcd) {
repeatCount = duration / gcd;
} else {
repeatCount = 1;
}
for (size_t i = 0; i < repeatCount; ++i) {
[animatedImages addObject:image];
}
}];
animatedImage = [UIImage animatedImageWithImages:animatedImages duration:totalDuration / 1000.f];
#else
NSMutableData *imageData = [NSMutableData data];
CFStringRef imageUTType = [NSData sd_UTTypeFromSDImageFormat:SDImageFormatGIF];
// Create an image destination. GIF 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++) {
@autoreleasepool {
SDWebImageFrame *frame = frames[i];
float frameDuration = frame.duration;
CGImageRef frameImageRef = frame.image.CGImage;
NSDictionary *frameProperties = @{(__bridge_transfer NSString *)kCGImagePropertyGIFDictionary : @{(__bridge_transfer NSString *)kCGImagePropertyGIFUnclampedDelayTime : @(frameDuration)}};
CGImageDestinationAddImage(imageDestination, frameImageRef, (__bridge CFDictionaryRef)frameProperties);
}
}
// Finalize the destination.
if (CGImageDestinationFinalize(imageDestination) == NO) {
// Handle failure.
CFRelease(imageDestination);
return nil;
}
CFRelease(imageDestination);
animatedImage = [[NSImage alloc] initWithData:imageData];
#endif
return animatedImage;
}
返回一个frames array，gif图片转换成一个帧数组
+ (NSArray<SDWebImageFrame *> *)framesFromAnimatedImage:(UIImage *)animatedImage {
if (!animatedImage) {
return nil;
}
NSMutableArray<SDWebImageFrame *> *frames = [NSMutableArray array];
NSUInteger frameCount = 0;
#if SD_UIKIT || SD_WATCH
NSArray<UIImage *> *animatedImages = animatedImage.images;
frameCount = animatedImages.count;
if (frameCount == 0) {
return nil;
}
NSTimeInterval avgDuration = animatedImage.duration / frameCount;
if (avgDuration == 0) {
avgDuration = 0.1; // if it's a animated image but no duration, set it to default 100ms (this do not have that 10ms limit like GIF or WebP to allow custom coder provide the limit)
}
__block NSUInteger index = 0;
__block NSUInteger repeatCount = 1;
__block UIImage *previousImage = animatedImages.firstObject;
[animatedImages enumerateObjectsUsingBlock:^(UIImage * _Nonnull image, NSUInteger idx, BOOL * _Nonnull stop) {
// ignore first
if (idx == 0) {
return;
}
if ([image isEqual:previousImage]) {
repeatCount++;
} else {
SDWebImageFrame *frame = [SDWebImageFrame frameWithImage:previousImage duration:avgDuration * repeatCount];
[frames addObject:frame];
repeatCount = 1;
index++;
}
previousImage = image;
// last one
if (idx == frameCount - 1) {
SDWebImageFrame *frame = [SDWebImageFrame frameWithImage:previousImage duration:avgDuration * repeatCount];
[frames addObject:frame];
}
}];
#else
NSBitmapImageRep *bitmapRep;
for (NSImageRep *imageRep in animatedImage.representations) {
if ([imageRep isKindOfClass:[NSBitmapImageRep class]]) {
bitmapRep = (NSBitmapImageRep *)imageRep;
break;
}
}
if (bitmapRep) {
frameCount = [[bitmapRep valueForProperty:NSImageFrameCount] unsignedIntegerValue];
}
if (frameCount == 0) {
return nil;
}
for (size_t i = 0; i < frameCount; i++) {
@autoreleasepool {
// NSBitmapImageRep need to manually change frame. "Good taste" API
[bitmapRep setProperty:NSImageCurrentFrame withValue:@(i)];
float frameDuration = [[bitmapRep valueForProperty:NSImageCurrentFrameDuration] floatValue];
NSImage *frameImage = [[NSImage alloc] initWithCGImage:bitmapRep.CGImage size:CGSizeZero];
SDWebImageFrame *frame = [SDWebImageFrame frameWithImage:frameImage duration:frameDuration];
[frames addObject:frame];
}
}
#endif
return frames;
}
转换方向信息
+ (UIImageOrientation)imageOrientationFromEXIFOrientation:(NSInteger)exifOrientation {
// CGImagePropertyOrientation is available on iOS 8 above. Currently kept for compatibility
UIImageOrientation imageOrientation = UIImageOrientationUp;
switch (exifOrientation) {
case 1:
imageOrientation = UIImageOrientationUp;
break;
case 3:
imageOrientation = UIImageOrientationDown;
break;
case 8:
imageOrientation = UIImageOrientationLeft;
break;
case 6:
imageOrientation = UIImageOrientationRight;
break;
case 2:
imageOrientation = UIImageOrientationUpMirrored;
break;
case 4:
imageOrientation = UIImageOrientationDownMirrored;
break;
case 5:
imageOrientation = UIImageOrientationLeftMirrored;
break;
case 7:
imageOrientation = UIImageOrientationRightMirrored;
break;
default:
break;
}
return imageOrientation;
}
+ (NSInteger)exifOrientationFromImageOrientation:(UIImageOrientation)imageOrientation {
// CGImagePropertyOrientation is available on iOS 8 above. Currently kept for compatibility
NSInteger exifOrientation = 1;
switch (imageOrientation) {
case UIImageOrientationUp:
exifOrientation = 1;
break;
case UIImageOrientationDown:
exifOrientation = 3;
break;
case UIImageOrientationLeft:
exifOrientation = 8;
break;
case UIImageOrientationRight:
exifOrientation = 6;
break;
case UIImageOrientationUpMirrored:
exifOrientation = 2;
break;
case UIImageOrientationDownMirrored:
exifOrientation = 4;
break;
case UIImageOrientationLeftMirrored:
exifOrientation = 5;
break;
case UIImageOrientationRightMirrored:
exifOrientation = 7;
break;
default:
break;
}
return exifOrientation;
}
完结
