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）
13. YYKit源码探究（十三） —— UIImage分类之框架结构和Create image部分（一）
14. YYKit源码探究（十四） —— UIImage分类之Image Info（二）
15. YYKit源码探究（十五） —— UIImage分类之Modify Image（三）

回顾

上一篇主要介绍了UIImage分类的Modify Image，这一篇我们就看一下Image Effect部分。

API

下面看一下API。

/**
 Tint the image in alpha channel with the given color.
 
 @param color  The color.
 */
- (nullable UIImage *)imageByTintColor:(UIColor *)color;

/**
 Returns a grayscaled image.
 */
- (nullable UIImage *)imageByGrayscale;

/**
 Applies a blur effect to this image. Suitable for blur any content.
 */
- (nullable UIImage *)imageByBlurSoft;

/**
 Applies a blur effect to this image. Suitable for blur any content except pure white.
 (same as iOS Control Panel)
 */
- (nullable UIImage *)imageByBlurLight;

/**
 Applies a blur effect to this image. Suitable for displaying black text.
 (same as iOS Navigation Bar White)
 */
- (nullable UIImage *)imageByBlurExtraLight;

/**
 Applies a blur effect to this image. Suitable for displaying white text.
 (same as iOS Notification Center)
 */
- (nullable UIImage *)imageByBlurDark;

/**
 Applies a blur and tint color to this image.
 
 @param tintColor  The tint color.
 */
- (nullable UIImage *)imageByBlurWithTint:(UIColor *)tintColor;

/**
 Applies a blur, tint color, and saturation adjustment to this image,
 optionally within the area specified by @a maskImage.
 
 @param blurRadius     The radius of the blur in points, 0 means no blur effect.
 
 @param tintColor      An optional UIColor object that is uniformly blended with
                       the result of the blur and saturation operations. The
                       alpha channel of this color determines how strong the
                       tint is. nil means no tint.
 
 @param tintBlendMode  The @a tintColor blend mode. Default is kCGBlendModeNormal (0).
 
 @param saturation     A value of 1.0 produces no change in the resulting image.
                       Values less than 1.0 will desaturation the resulting image
                       while values greater than 1.0 will have the opposite effect.
                       0 means gray scale.
 
 @param maskImage      If specified, @a inputImage is only modified in the area(s)
                       defined by this mask.  This must be an image mask or it
                       must meet the requirements of the mask parameter of
                       CGContextClipToMask.
 
 @return               image with effect, or nil if an error occurs (e.g. no
                       enough memory).
 */
- (nullable UIImage *)imageByBlurRadius:(CGFloat)blurRadius
                              tintColor:(nullable UIColor *)tintColor
                               tintMode:(CGBlendMode)tintBlendMode
                             saturation:(CGFloat)saturation
                              maskImage:(nullable UIImage *)maskImage;

1. - (nullable UIImage *)imageByTintColor:(UIColor *)color;

该方法的作用就是用给定颜色在alpha通道中对图像着色。

方法实现

- (UIImage *)imageByTintColor:(UIColor *)color {
    UIGraphicsBeginImageContextWithOptions(self.size, NO, self.scale);
    CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
    [color set];
    UIRectFill(rect);
    [self drawAtPoint:CGPointMake(0, 0) blendMode:kCGBlendModeDestinationIn alpha:1];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

2. - (nullable UIImage *)imageByGrayscale;

该方法的作用就是返回一个返回灰度图像。

方法实现

- (UIImage *)imageByGrayscale {
    return [self imageByBlurRadius:0 tintColor:nil tintMode:0 saturation:0 maskImage:nil];
}

- (UIImage *)imageByBlurRadius:(CGFloat)blurRadius
                     tintColor:(UIColor *)tintColor
                      tintMode:(CGBlendMode)tintBlendMode
                    saturation:(CGFloat)saturation
                     maskImage:(UIImage *)maskImage {
    if (self.size.width < 1 || self.size.height < 1) {
        NSLog(@"UIImage+YYAdd error: invalid size: (%.2f x %.2f). Both dimensions must be >= 1: %@", self.size.width, self.size.height, self);
        return nil;
    }
    if (!self.CGImage) {
        NSLog(@"UIImage+YYAdd error: inputImage must be backed by a CGImage: %@", self);
        return nil;
    }
    if (maskImage && !maskImage.CGImage) {
        NSLog(@"UIImage+YYAdd error: effectMaskImage must be backed by a CGImage: %@", maskImage);
        return nil;
    }
    
    // iOS7 and above can use new func.
    BOOL hasNewFunc = (long)vImageBuffer_InitWithCGImage != 0 && (long)vImageCreateCGImageFromBuffer != 0;
    BOOL hasBlur = blurRadius > __FLT_EPSILON__;
    BOOL hasSaturation = fabs(saturation - 1.0) > __FLT_EPSILON__;
    
    CGSize size = self.size;
    CGRect rect = { CGPointZero, size };
    CGFloat scale = self.scale;
    CGImageRef imageRef = self.CGImage;
    BOOL opaque = NO;
    
    if (!hasBlur && !hasSaturation) {
        return [self _yy_mergeImageRef:imageRef tintColor:tintColor tintBlendMode:tintBlendMode maskImage:maskImage opaque:opaque];
    }
    
    vImage_Buffer effect = { 0 }, scratch = { 0 };
    vImage_Buffer *input = NULL, *output = NULL;
    
    vImage_CGImageFormat format = {
        .bitsPerComponent = 8,
        .bitsPerPixel = 32,
        .colorSpace = NULL,
        .bitmapInfo = kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Little, //requests a BGRA buffer.
        .version = 0,
        .decode = NULL,
        .renderingIntent = kCGRenderingIntentDefault
    };
    
    if (hasNewFunc) {
        vImage_Error err;
        err = vImageBuffer_InitWithCGImage(&effect, &format, NULL, imageRef, kvImagePrintDiagnosticsToConsole);
        if (err != kvImageNoError) {
            NSLog(@"UIImage+YYAdd error: vImageBuffer_InitWithCGImage returned error code %zi for inputImage: %@", err, self);
            return nil;
        }
        err = vImageBuffer_Init(&scratch, effect.height, effect.width, format.bitsPerPixel, kvImageNoFlags);
        if (err != kvImageNoError) {
            NSLog(@"UIImage+YYAdd error: vImageBuffer_Init returned error code %zi for inputImage: %@", err, self);
            return nil;
        }
    } else {
        UIGraphicsBeginImageContextWithOptions(size, opaque, scale);
        CGContextRef effectCtx = UIGraphicsGetCurrentContext();
        CGContextScaleCTM(effectCtx, 1.0, -1.0);
        CGContextTranslateCTM(effectCtx, 0, -size.height);
        CGContextDrawImage(effectCtx, rect, imageRef);
        effect.data     = CGBitmapContextGetData(effectCtx);
        effect.width    = CGBitmapContextGetWidth(effectCtx);
        effect.height   = CGBitmapContextGetHeight(effectCtx);
        effect.rowBytes = CGBitmapContextGetBytesPerRow(effectCtx);
        
        UIGraphicsBeginImageContextWithOptions(size, opaque, scale);
        CGContextRef scratchCtx = UIGraphicsGetCurrentContext();
        scratch.data     = CGBitmapContextGetData(scratchCtx);
        scratch.width    = CGBitmapContextGetWidth(scratchCtx);
        scratch.height   = CGBitmapContextGetHeight(scratchCtx);
        scratch.rowBytes = CGBitmapContextGetBytesPerRow(scratchCtx);
    }
    
    input = &effect;
    output = &scratch;
    
    if (hasBlur) {
        // A description of how to compute the box kernel width from the Gaussian
        // radius (aka standard deviation) appears in the SVG spec:
        // http://www.w3.org/TR/SVG/filters.html#feGaussianBlurElement
        //
        // For larger values of 's' (s >= 2.0), an approximation can be used: Three
        // successive box-blurs build a piece-wise quadratic convolution kernel, which
        // approximates the Gaussian kernel to within roughly 3%.
        //
        // let d = floor(s * 3*sqrt(2*pi)/4 + 0.5)
        //
        // ... if d is odd, use three box-blurs of size 'd', centered on the output pixel.
        //
        CGFloat inputRadius = blurRadius * scale;
        if (inputRadius - 2.0 < __FLT_EPSILON__) inputRadius = 2.0;
        uint32_t radius = floor((inputRadius * 3.0 * sqrt(2 * M_PI) / 4 + 0.5) / 2);
        radius |= 1; // force radius to be odd so that the three box-blur methodology works.
        int iterations;
        if (blurRadius * scale < 0.5) iterations = 1;
        else if (blurRadius * scale < 1.5) iterations = 2;
        else iterations = 3;
        NSInteger tempSize = vImageBoxConvolve_ARGB8888(input, output, NULL, 0, 0, radius, radius, NULL, kvImageGetTempBufferSize | kvImageEdgeExtend);
        void *temp = malloc(tempSize);
        for (int i = 0; i < iterations; i++) {
            vImageBoxConvolve_ARGB8888(input, output, temp, 0, 0, radius, radius, NULL, kvImageEdgeExtend);
            YY_SWAP(input, output);
        }
        free(temp);
    }
    
    
    if (hasSaturation) {
        // These values appear in the W3C Filter Effects spec:
        // https://dvcs.w3.org/hg/FXTF/raw-file/default/filters/Publish.html#grayscaleEquivalent
        CGFloat s = saturation;
        CGFloat matrixFloat[] = {
            0.0722 + 0.9278 * s,  0.0722 - 0.0722 * s,  0.0722 - 0.0722 * s,  0,
            0.7152 - 0.7152 * s,  0.7152 + 0.2848 * s,  0.7152 - 0.7152 * s,  0,
            0.2126 - 0.2126 * s,  0.2126 - 0.2126 * s,  0.2126 + 0.7873 * s,  0,
            0,                    0,                    0,                    1,
        };
        const int32_t divisor = 256;
        NSUInteger matrixSize = sizeof(matrixFloat) / sizeof(matrixFloat[0]);
        int16_t matrix[matrixSize];
        for (NSUInteger i = 0; i < matrixSize; ++i) {
            matrix[i] = (int16_t)roundf(matrixFloat[i] * divisor);
        }
        vImageMatrixMultiply_ARGB8888(input, output, matrix, divisor, NULL, NULL, kvImageNoFlags);
        YY_SWAP(input, output);
    }
    
    UIImage *outputImage = nil;
    if (hasNewFunc) {
        CGImageRef effectCGImage = NULL;
        effectCGImage = vImageCreateCGImageFromBuffer(input, &format, &_yy_cleanupBuffer, NULL, kvImageNoAllocate, NULL);
        if (effectCGImage == NULL) {
            effectCGImage = vImageCreateCGImageFromBuffer(input, &format, NULL, NULL, kvImageNoFlags, NULL);
            free(input->data);
        }
        free(output->data);
        outputImage = [self _yy_mergeImageRef:effectCGImage tintColor:tintColor tintBlendMode:tintBlendMode maskImage:maskImage opaque:opaque];
        CGImageRelease(effectCGImage);
    } else {
        CGImageRef effectCGImage;
        UIImage *effectImage;
        if (input != &effect) effectImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        if (input == &effect) effectImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        effectCGImage = effectImage.CGImage;
        outputImage = [self _yy_mergeImageRef:effectCGImage tintColor:tintColor tintBlendMode:tintBlendMode maskImage:maskImage opaque:opaque];
    }
    return outputImage;
}

// Helper function to add tint and mask.
- (UIImage *)_yy_mergeImageRef:(CGImageRef)effectCGImage
                     tintColor:(UIColor *)tintColor
                 tintBlendMode:(CGBlendMode)tintBlendMode
                     maskImage:(UIImage *)maskImage
                        opaque:(BOOL)opaque {
    BOOL hasTint = tintColor != nil && CGColorGetAlpha(tintColor.CGColor) > __FLT_EPSILON__;
    BOOL hasMask = maskImage != nil;
    CGSize size = self.size;
    CGRect rect = { CGPointZero, size };
    CGFloat scale = self.scale;
    
    if (!hasTint && !hasMask) {
        return [UIImage imageWithCGImage:effectCGImage];
    }
    
    UIGraphicsBeginImageContextWithOptions(size, opaque, scale);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextScaleCTM(context, 1.0, -1.0);
    CGContextTranslateCTM(context, 0, -size.height);
    if (hasMask) {
        CGContextDrawImage(context, rect, self.CGImage);
        CGContextSaveGState(context);
        CGContextClipToMask(context, rect, maskImage.CGImage);
    }
    CGContextDrawImage(context, rect, effectCGImage);
    if (hasTint) {
        CGContextSaveGState(context);
        CGContextSetBlendMode(context, tintBlendMode);
        CGContextSetFillColorWithColor(context, tintColor.CGColor);
        CGContextFillRect(context, rect);
        CGContextRestoreGState(context);
    }
    if (hasMask) {
        CGContextRestoreGState(context);
    }
    UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return outputImage;
}

3. - (nullable UIImage *)imageByBlurSoft;

该方法的作用就是对此图像应用模糊效果。 适合模糊任何内容。

方法实现

- (UIImage *)imageByBlurSoft {
    return [self imageByBlurRadius:60 tintColor:[UIColor colorWithWhite:0.84 alpha:0.36] tintMode:kCGBlendModeNormal saturation:1.8 maskImage:nil];
}

这里调用的方法与2中调用的方法是一样的，不同的就是传入的参数值不同。

4. - (nullable UIImage *)imageByBlurLight;

该方法的作用就是对此图像应用模糊效果。 适用于模糊除纯白色以外的任何内容。（与iOS控制面板相同）

方法实现

- (UIImage *)imageByBlurLight {
    return [self imageByBlurRadius:60 tintColor:[UIColor colorWithWhite:1.0 alpha:0.3] tintMode:kCGBlendModeNormal saturation:1.8 maskImage:nil];
}

这里调用的方法与2中调用的方法是一样的，不同的就是传入的参数值不同。

5. - (nullable UIImage *)imageByBlurExtraLight;

该方法的作用就是对此图像应用模糊效果。 适合显示黑色文本，（与iOS导航栏白色相同）。

方法实现

- (UIImage *)imageByBlurExtraLight {
    return [self imageByBlurRadius:40 tintColor:[UIColor colorWithWhite:0.97 alpha:0.82] tintMode:kCGBlendModeNormal saturation:1.8 maskImage:nil];
}

6. - (nullable UIImage *)imageByBlurDark;

该方法的作用就是对此图像应用模糊效果。 适合显示白色文本， （与iOS通知中心相同）

方法实现

- (UIImage *)imageByBlurDark {
    return [self imageByBlurRadius:40 tintColor:[UIColor colorWithWhite:0.11 alpha:0.73] tintMode:kCGBlendModeNormal saturation:1.8 maskImage:nil];
}

7. - (nullable UIImage *)imageByBlurWithTint:(UIColor *)tintColor;

该方法的作用就是为此图像应用模糊和色调颜色。

方法实现

- (UIImage *)imageByBlurWithTint:(UIColor *)tintColor {
    const CGFloat EffectColorAlpha = 0.6;
    UIColor *effectColor = tintColor;
    size_t componentCount = CGColorGetNumberOfComponents(tintColor.CGColor);
    if (componentCount == 2) {
        CGFloat b;
        if ([tintColor getWhite:&b alpha:NULL]) {
            effectColor = [UIColor colorWithWhite:b alpha:EffectColorAlpha];
        }
    } else {
        CGFloat r, g, b;
        if ([tintColor getRed:&r green:&g blue:&b alpha:NULL]) {
            effectColor = [UIColor colorWithRed:r green:g blue:b alpha:EffectColorAlpha];
        }
    }
    return [self imageByBlurRadius:20 tintColor:effectColor tintMode:kCGBlendModeNormal saturation:-1.0 maskImage:nil];
}

8. - (nullable UIImage *)imageByBlurRadius:(CGFloat)blurRadius tintColor:(nullable UIColor *)tintColor tintMode:(CGBlendMode)tintBlendMode saturation:(CGFloat)saturation maskImage:(nullable UIImage *)maskImage;

大家对这个方法应该不是很陌生吧，前面很多地方都调用了这个方法。

该方法的作用就是对此图像应用模糊，色调和饱和度调整，可选地在由maskImage指定的区域内。

• blurRadius：模糊点的半径，0表示没有模糊效果。
• tintColor：与模糊和饱和度操作的结果均匀混合的可选UIColor对象。 这种颜色的alpha通道决定着色的强度。 nil意味着没有色彩。
• tintBlendMode：@a tintColor混合模式。 默认是kCGBlendModeNormal（0）
• saturation：1.0的值在结果图像中不产生变化。 小于1.0的值会使得到的图像去饱和，而大于1.0的值则会产生相反的效果。 0表示灰度。
• maskImage：如果指定，则@a inputImage仅在由此掩码定义的区域中进行修改。 这必须是一个图像掩码，或者它必须满足CGContextClipToMask的掩码参数的要求。

这里具体如何实现就不贴出来了，前面已经贴出来过了。

后记

本篇主要介绍了UIImage分类的Image Effect，感兴趣的给个赞或者关注，谢谢~~~