版本记录

前言

iOS圈内有几个人大家基本都知道，比如说王巍、唐巧，还有YYKit框架的作者现任职于滴滴的郭曜源 - ibireme等。这里有一篇唐巧对他的专访，还有他的 GitHub - Yaoyuan 和 博客，这里贴出来框架YYKit 框架。接下来几篇我们就一起来看一下这个框架。感兴趣的可以看上面写的几篇。
1. YYKit源码探究（一） —— 基本概览
2. YYKit源码探究（二） —— NSString分类之Hash（一）
3. YYKit源码探究（三） —— NSString分类之Encode and decode（二）
4. YYKit源码探究（四） —— NSString分类之Drawing（三）
5. YYKit源码探究（五） —— NSString分类之Regular Expression（四）
6. YYKit源码探究（六） —— NSString分类之NSNumber Compatible（五）
7. YYKit源码探究（七） —— NSString分类之Utilities（六）
8. YYKit源码探究（八） —— NSNumber分类（一）
9. YYKit源码探究（九） —— UIFont分类之架构分析和Font Traits（一）
10. YYKit源码探究（十） —— UIFont分类之Create font（二）
11. YYKit源码探究（十一） —— UIFont分类之Load and unload font（三）
12. YYKit源码探究（十二） —— UIFont分类之Dump font data（四）

回顾

上一篇主要介绍了UIFont分类的部分，这一篇我们就看一下UIImage分类部分。

框架结构

下面我们看一下框架的结构。

Create image API接口

下面我们看一下API接口。

/**
 Create an animated image with GIF data. After created, you can access
 the images via property '.images'. If the data is not animated gif, this
 function is same as [UIImage imageWithData:data scale:scale];
 
 @discussion     It has a better display performance, but costs more memory
                 (width * height * frames Bytes). It only suited to display small 
                 gif such as animated emoticon. If you want to display large gif, 
                 see `YYImage`.
 
 @param data     GIF data.
 
 @param scale    The scale factor
 
 @return A new image created from GIF, or nil when an error occurs.
 */
+ (nullable UIImage *)imageWithSmallGIFData:(NSData *)data scale:(CGFloat)scale;

/**
 Whether the data is animated GIF.
 
 @param data Image data
 
 @return Returns YES only if the data is gif and contains more than one frame,
         otherwise returns NO.
 */
+ (BOOL)isAnimatedGIFData:(NSData *)data;

/**
 Whether the file in the specified path is GIF.
 
 @param path An absolute file path.
 
 @return Returns YES if the file is gif, otherwise returns NO.
 */
+ (BOOL)isAnimatedGIFFile:(NSString *)path;

/**
 Create an image from a PDF file data or path.
 
 @discussion If the PDF has multiple page, is just return's the first page's
 content. Image's scale is equal to current screen's scale, size is same as 
 PDF's origin size.
 
 @param dataOrPath PDF data in `NSData`, or PDF file path in `NSString`.
 
 @return A new image create from PDF, or nil when an error occurs.
 */
+ (nullable UIImage *)imageWithPDF:(id)dataOrPath;

/**
 Create an image from a PDF file data or path.
 
 @discussion If the PDF has multiple page, is just return's the first page's
 content. Image's scale is equal to current screen's scale.
 
 @param dataOrPath  PDF data in `NSData`, or PDF file path in `NSString`.
 
 @param size     The new image's size, PDF's content will be stretched as needed.
 
 @return A new image create from PDF, or nil when an error occurs.
 */
+ (nullable UIImage *)imageWithPDF:(id)dataOrPath size:(CGSize)size;

/**
 Create a square image from apple emoji.
 
 @discussion It creates a square image from apple emoji, image's scale is equal
 to current screen's scale. The original emoji image in `AppleColorEmoji` font 
 is in size 160*160 px.
 
 @param emoji single emoji, such as @"😄".
 
 @param size  image's size.
 
 @return Image from emoji, or nil when an error occurs.
 */
+ (nullable UIImage *)imageWithEmoji:(NSString *)emoji size:(CGFloat)size;

/**
 Create and return a 1x1 point size image with the given color.
 
 @param color  The color.
 */
+ (nullable UIImage *)imageWithColor:(UIColor *)color;

/**
 Create and return a pure color image with the given color and size.
 
 @param color  The color.
 @param size   New image's type.
 */
+ (nullable UIImage *)imageWithColor:(UIColor *)color size:(CGSize)size;

/**
 Create and return an image with custom draw code.
 
 @param size      The image size.
 @param drawBlock The draw block.
 
 @return The new image.
 */
+ (nullable UIImage *)imageWithSize:(CGSize)size drawBlock:(void (^)(CGContextRef context))drawBlock;

1. + (nullable UIImage *)imageWithSmallGIFData:(NSData *)data scale:(CGFloat)scale;

该方法的作用是，根据GIF data对象创建动画图像。在创建之后，你可以通过属性.images获取images，如果data不是动画GIF，这个功能和[UIImage imageWithData:data scale:scale]是一样的。

它具有更好的显示性能，但成本更高（宽高帧字节）。 它只适用于显示动画表情符号等小gif。 如果你想显示大的gif，请参阅YYImage。

下面我们看一下该方法的实现。

+ (UIImage *)imageWithSmallGIFData:(NSData *)data scale:(CGFloat)scale {
    CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFTypeRef)(data), NULL);
    if (!source) return nil;
    
    size_t count = CGImageSourceGetCount(source);
    if (count <= 1) {
        CFRelease(source);
        return [self.class imageWithData:data scale:scale];
    }
    
    NSUInteger frames[count];
    double oneFrameTime = 1 / 50.0; // 50 fps
    NSTimeInterval totalTime = 0;
    NSUInteger totalFrame = 0;
    NSUInteger gcdFrame = 0;
    for (size_t i = 0; i < count; i++) {
        NSTimeInterval delay = _yy_CGImageSourceGetGIFFrameDelayAtIndex(source, i);
        totalTime += delay;
        NSInteger frame = lrint(delay / oneFrameTime);
        if (frame < 1) frame = 1;
        frames[i] = frame;
        totalFrame += frames[i];
        if (i == 0) gcdFrame = frames[i];
        else {
            NSUInteger frame = frames[i], tmp;
            if (frame < gcdFrame) {
                tmp = frame; frame = gcdFrame; gcdFrame = tmp;
            }
            while (true) {
                tmp = frame % gcdFrame;
                if (tmp == 0) break;
                frame = gcdFrame;
                gcdFrame = tmp;
            }
        }
    }
    NSMutableArray *array = [NSMutableArray new];
    for (size_t i = 0; i < count; i++) {
        CGImageRef imageRef = CGImageSourceCreateImageAtIndex(source, i, NULL);
        if (!imageRef) {
            CFRelease(source);
            return nil;
        }
        size_t width = CGImageGetWidth(imageRef);
        size_t height = CGImageGetHeight(imageRef);
        if (width == 0 || height == 0) {
            CFRelease(source);
            CFRelease(imageRef);
            return nil;
        }
        
        CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(imageRef) & kCGBitmapAlphaInfoMask;
        BOOL hasAlpha = NO;
        if (alphaInfo == kCGImageAlphaPremultipliedLast ||
            alphaInfo == kCGImageAlphaPremultipliedFirst ||
            alphaInfo == kCGImageAlphaLast ||
            alphaInfo == kCGImageAlphaFirst) {
            hasAlpha = YES;
        }
        // BGRA8888 (premultiplied) or BGRX8888
        // same as UIGraphicsBeginImageContext() and -[UIView drawRect:]
        CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Host;
        bitmapInfo |= hasAlpha ? kCGImageAlphaPremultipliedFirst : kCGImageAlphaNoneSkipFirst;
        CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
        CGContextRef context = CGBitmapContextCreate(NULL, width, height, 8, 0, space, bitmapInfo);
        CGColorSpaceRelease(space);
        if (!context) {
            CFRelease(source);
            CFRelease(imageRef);
            return nil;
        }
        CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef); // decode
        CGImageRef decoded = CGBitmapContextCreateImage(context);
        CFRelease(context);
        if (!decoded) {
            CFRelease(source);
            CFRelease(imageRef);
            return nil;
        }
        UIImage *image = [UIImage imageWithCGImage:decoded scale:scale orientation:UIImageOrientationUp];
        CGImageRelease(imageRef);
        CGImageRelease(decoded);
        if (!image) {
            CFRelease(source);
            return nil;
        }
        for (size_t j = 0, max = frames[i] / gcdFrame; j < max; j++) {
            [array addObject:image];
        }
    }
    CFRelease(source);
    UIImage *image = [self.class animatedImageWithImages:array duration:totalTime];
    return image;
}

2. + (BOOL)isAnimatedGIFData:(NSData *)data;

用来判断是否data是动画GIF，如果data是GIF并且包含超过一帧就返回YES，否则返回NO。

下面看一下方法的实现。

+ (BOOL)isAnimatedGIFData:(NSData *)data {
    if (data.length < 16) return NO;
    UInt32 magic = *(UInt32 *)data.bytes;
    // http://www.w3.org/Graphics/GIF/spec-gif89a.txt
    if ((magic & 0xFFFFFF) != '\0FIG') return NO;
    CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFTypeRef)data, NULL);
    if (!source) return NO;
    size_t count = CGImageSourceGetCount(source);
    CFRelease(source);
    return count > 1;
}

3. + (BOOL)isAnimatedGIFFile:(NSString *)path;

该方法的作用就是判断指定路径的文件是否是GIF。

下面我们就看下方法的实现。

+ (BOOL)isAnimatedGIFFile:(NSString *)path {
    if (path.length == 0) return NO;
    const char *cpath = path.UTF8String;
    FILE *fd = fopen(cpath, "rb");
    if (!fd) return NO;
    
    BOOL isGIF = NO;
    UInt32 magic = 0;
    if (fread(&magic, sizeof(UInt32), 1, fd) == 1) {
        if ((magic & 0xFFFFFF) == '\0FIG') isGIF = YES;
    }
    fclose(fd);
    return isGIF;
}

4. + (nullable UIImage *)imageWithPDF:(id)dataOrPath;

该方法的作用就是根据PDF文件数据data或者路径创建image。如果PDF有多个页面，则只是返回第一页的内容。 图像的比例等于当前屏幕的比例，尺寸与PDF的原始尺寸相同。参数dataOrPath的作用是NSData类型的PDF数据或者NSString类型的文件路径。

下面看一下方法的实现。

+ (UIImage *)imageWithPDF:(id)dataOrPath {
    return [self _yy_imageWithPDF:dataOrPath resize:NO size:CGSizeZero];
}

+ (UIImage *)_yy_imageWithPDF:(id)dataOrPath resize:(BOOL)resize size:(CGSize)size {
    CGPDFDocumentRef pdf = NULL;
    if ([dataOrPath isKindOfClass:[NSData class]]) {
        CGDataProviderRef provider = CGDataProviderCreateWithCFData((__bridge CFDataRef)dataOrPath);
        pdf = CGPDFDocumentCreateWithProvider(provider);
        CGDataProviderRelease(provider);
    } else if ([dataOrPath isKindOfClass:[NSString class]]) {
        pdf = CGPDFDocumentCreateWithURL((__bridge CFURLRef)[NSURL fileURLWithPath:dataOrPath]);
    }
    if (!pdf) return nil;
    
    CGPDFPageRef page = CGPDFDocumentGetPage(pdf, 1);
    if (!page) {
        CGPDFDocumentRelease(pdf);
        return nil;
    }
    
    CGRect pdfRect = CGPDFPageGetBoxRect(page, kCGPDFCropBox);
    CGSize pdfSize = resize ? size : pdfRect.size;
    CGFloat scale = [UIScreen mainScreen].scale;
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef ctx = CGBitmapContextCreate(NULL, pdfSize.width * scale, pdfSize.height * scale, 8, 0, colorSpace, kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedFirst);
    if (!ctx) {
        CGColorSpaceRelease(colorSpace);
        CGPDFDocumentRelease(pdf);
        return nil;
    }
    
    CGContextScaleCTM(ctx, scale, scale);
    CGContextTranslateCTM(ctx, -pdfRect.origin.x, -pdfRect.origin.y);
    CGContextDrawPDFPage(ctx, page);
    CGPDFDocumentRelease(pdf);
    
    CGImageRef image = CGBitmapContextCreateImage(ctx);
    UIImage *pdfImage = [[UIImage alloc] initWithCGImage:image scale:scale orientation:UIImageOrientationUp];
    CGImageRelease(image);
    CGContextRelease(ctx);
    CGColorSpaceRelease(colorSpace);
    
    return pdfImage;
}

5. + (nullable UIImage *)imageWithPDF:(id)dataOrPath size:(CGSize)size;

该方法的作用就是根据指定的PDF文件数据或者路径创建图像image。如果PDF有多个页面，则只是返回第一页的内容。 图像的比例等于当前屏幕的比例。参数size的意义是新图片的大小，PDF的内容将根据需要延展。

下面看一下方法的实现。

+ (UIImage *)imageWithPDF:(id)dataOrPath size:(CGSize)size {
    return [self _yy_imageWithPDF:dataOrPath resize:YES size:size];
}

调用的方法和上面的是一样的。

6. + (nullable UIImage *)imageWithEmoji:(NSString *)emoji size:(CGFloat)size;

该方法的作用是，从苹果表情符创建一个方形图像。它从苹果表情符创建一个方形图像，图像比例等于当前屏幕的比例。 Apple Color Emoji字体中的原始表情符号图像大小为160 * 160像素。

下面我们看一下方法的实现。

+ (UIImage *)imageWithEmoji:(NSString *)emoji size:(CGFloat)size {
    if (emoji.length == 0) return nil;
    if (size < 1) return nil;
    
    CGFloat scale = [UIScreen mainScreen].scale;
    CTFontRef font = CTFontCreateWithName(CFSTR("AppleColorEmoji"), size * scale, NULL);
    if (!font) return nil;
    
    NSAttributedString *str = [[NSAttributedString alloc] initWithString:emoji attributes:@{ (__bridge id)kCTFontAttributeName:(__bridge id)font, (__bridge id)kCTForegroundColorAttributeName:(__bridge id)[UIColor whiteColor].CGColor }];
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef ctx = CGBitmapContextCreate(NULL, size * scale, size * scale, 8, 0, colorSpace, kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedFirst);
    CGContextSetInterpolationQuality(ctx, kCGInterpolationHigh);
    CTLineRef line = CTLineCreateWithAttributedString((__bridge CFTypeRef)str);
    CGRect bounds = CTLineGetBoundsWithOptions(line, kCTLineBoundsUseGlyphPathBounds);
    CGContextSetTextPosition(ctx, 0, -bounds.origin.y);
    CTLineDraw(line, ctx);
    CGImageRef imageRef = CGBitmapContextCreateImage(ctx);
    UIImage *image = [[UIImage alloc] initWithCGImage:imageRef scale:scale orientation:UIImageOrientationUp];
    
    CFRelease(font);
    CGColorSpaceRelease(colorSpace);
    CGContextRelease(ctx);
    if (line)CFRelease(line);
    if (imageRef) CFRelease(imageRef);
    
    return image;
}

7. + (nullable UIImage *)imageWithColor:(UIColor *)color;

该方法的作用就是用给定的颜色创建并返回1x1点大小的图像。

下面看一下方法的实现。

+ (UIImage *)imageWithColor:(UIColor *)color {
    return [self imageWithColor:color size:CGSizeMake(1, 1)];
}

+ (UIImage *)imageWithColor:(UIColor *)color size:(CGSize)size {
    if (!color || size.width <= 0 || size.height <= 0) return nil;
    CGRect rect = CGRectMake(0.0f, 0.0f, size.width, size.height);
    UIGraphicsBeginImageContextWithOptions(rect.size, NO, 0);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, color.CGColor);
    CGContextFillRect(context, rect);
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

8. + (nullable UIImage *)imageWithColor:(UIColor *)color size:(CGSize)size;

该方法的作用就是创建并返回具有给定颜色和大小的纯色图像。

下面看一下方法的实现。

+ (UIImage *)imageWithColor:(UIColor *)color size:(CGSize)size {
    if (!color || size.width <= 0 || size.height <= 0) return nil;
    CGRect rect = CGRectMake(0.0f, 0.0f, size.width, size.height);
    UIGraphicsBeginImageContextWithOptions(rect.size, NO, 0);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, color.CGColor);
    CGContextFillRect(context, rect);
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

9. + (nullable UIImage *)imageWithSize:(CGSize)size drawBlock:(void (^)(CGContextRef context))drawBlock;

该方法的作用是用自定义绘图代码创建并返回图像。

下面看一下方法的实现。

+ (UIImage *)imageWithSize:(CGSize)size drawBlock:(void (^)(CGContextRef context))drawBlock {
    if (!drawBlock) return nil;
    UIGraphicsBeginImageContextWithOptions(size, NO, 0);
    CGContextRef context = UIGraphicsGetCurrentContext();
    if (!context) return nil;
    drawBlock(context);
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

后记

本篇主要介绍了UIImage分类的架构以及第一部分Create image，感兴趣的给个赞或者关注，谢谢~~~