版本记录

版本号	时间
V1.0	2018.03.25

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）

回顾

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

---

API

下面看一下API。

/**
 Draws the entire image in the specified rectangle, content changed with
 the contentMode.
 
 @discussion This method draws the entire image in the current graphics context, 
 respecting the image's orientation setting. In the default coordinate system, 
 images are situated down and to the right of the origin of the specified 
 rectangle. This method respects any transforms applied to the current graphics 
 context, however.
 
 @param rect        The rectangle in which to draw the image.
 
 @param contentMode Draw content mode
 
 @param clips       A Boolean value that determines whether content are confined to the rect.
 */
- (void)drawInRect:(CGRect)rect withContentMode:(UIViewContentMode)contentMode clipsToBounds:(BOOL)clips;

/**
 Returns a new image which is scaled from this image.
 The image will be stretched as needed.
 
 @param size  The new size to be scaled, values should be positive.
 
 @return      The new image with the given size.
 */
- (nullable UIImage *)imageByResizeToSize:(CGSize)size;

/**
 Returns a new image which is scaled from this image.
 The image content will be changed with thencontentMode.
 
 @param size        The new size to be scaled, values should be positive.
 
 @param contentMode The content mode for image content.
 
 @return The new image with the given size.
 */
- (nullable UIImage *)imageByResizeToSize:(CGSize)size contentMode:(UIViewContentMode)contentMode;

/**
 Returns a new image which is cropped from this image.
 
 @param rect  Image's inner rect.
 
 @return      The new image, or nil if an error occurs.
 */
- (nullable UIImage *)imageByCropToRect:(CGRect)rect;

/**
 Returns a new image which is edge inset from this image.
 
 @param insets  Inset (positive) for each of the edges, values can be negative to 'outset'.
 
 @param color   Extend edge's fill color, nil means clear color.
 
 @return        The new image, or nil if an error occurs.
 */
- (nullable UIImage *)imageByInsetEdge:(UIEdgeInsets)insets withColor:(nullable UIColor *)color;

/**
 Rounds a new image with a given corner size.
 
 @param radius  The radius of each corner oval. Values larger than half the
                rectangle's width or height are clamped appropriately to half
                the width or height.
 */
- (nullable UIImage *)imageByRoundCornerRadius:(CGFloat)radius;

/**
 Rounds a new image with a given corner size.
 
 @param radius       The radius of each corner oval. Values larger than half the
                     rectangle's width or height are clamped appropriately to
                     half the width or height.

 @param borderWidth  The inset border line width. Values larger than half the rectangle's
                     width or height are clamped appropriately to half the width 
                     or height.
 
 @param borderColor  The border stroke color. nil means clear color.
 */
- (nullable UIImage *)imageByRoundCornerRadius:(CGFloat)radius
                                   borderWidth:(CGFloat)borderWidth
                                   borderColor:(nullable UIColor *)borderColor;

/**
 Rounds a new image with a given corner size.
 
 @param radius       The radius of each corner oval. Values larger than half the
                     rectangle's width or height are clamped appropriately to
                     half the width or height.
 
 @param corners      A bitmask value that identifies the corners that you want
                     rounded. You can use this parameter to round only a subset
                     of the corners of the rectangle.
 
 @param borderWidth  The inset border line width. Values larger than half the rectangle's
                     width or height are clamped appropriately to half the width 
                     or height.
 
 @param borderColor  The border stroke color. nil means clear color.
 
 @param borderLineJoin The border line join.
 */
- (nullable UIImage *)imageByRoundCornerRadius:(CGFloat)radius
                                       corners:(UIRectCorner)corners
                                   borderWidth:(CGFloat)borderWidth
                                   borderColor:(nullable UIColor *)borderColor
                                borderLineJoin:(CGLineJoin)borderLineJoin;

/**
 Returns a new rotated image (relative to the center).
 
 @param radians   Rotated radians in counterclockwise.⟲
 
 @param fitSize   YES: new image's size is extend to fit all content.
                  NO: image's size will not change, content may be clipped.
 */
- (nullable UIImage *)imageByRotate:(CGFloat)radians fitSize:(BOOL)fitSize;

/**
 Returns a new image rotated counterclockwise by a quarter‑turn (90°). ⤺
 The width and height will be exchanged.
 */
- (nullable UIImage *)imageByRotateLeft90;

/**
 Returns a new image rotated clockwise by a quarter‑turn (90°). ⤼
 The width and height will be exchanged.
 */
- (nullable UIImage *)imageByRotateRight90;

/**
 Returns a new image rotated 180° . ↻
 */
- (nullable UIImage *)imageByRotate180;

/**
 Returns a vertically flipped image. ⥯
 */
- (nullable UIImage *)imageByFlipVertical;

/**
 Returns a horizontally flipped image. ⇋
 */
- (nullable UIImage *)imageByFlipHorizontal;

1. - (void)drawInRect:(CGRect)rect withContentMode:(UIViewContentMode)contentMode clipsToBounds:(BOOL)clips;

该方法的作用是在指定的矩形中绘制整个图像，使用contentMode更改内容。

此方法在当前图形上下文中绘制整个图像，并考虑图像的方向设置。 在默认坐标系中，图像位于指定矩形的原点的右下方。 但是，此方法应用于当前图形上下文的任何转换。

方法实现

- (void)drawInRect:(CGRect)rect withContentMode:(UIViewContentMode)contentMode clipsToBounds:(BOOL)clips{
    CGRect drawRect = YYCGRectFitWithContentMode(rect, self.size, contentMode);
    if (drawRect.size.width == 0 || drawRect.size.height == 0) return;
    if (clips) {
        CGContextRef context = UIGraphicsGetCurrentContext();
        if (context) {
            CGContextSaveGState(context);
            CGContextAddRect(context, rect);
            CGContextClip(context);
            [self drawInRect:drawRect];
            CGContextRestoreGState(context);
        }
    } else {
        [self drawInRect:drawRect];
    }
}

CGRect YYCGRectFitWithContentMode(CGRect rect, CGSize size, UIViewContentMode mode) {
    rect = CGRectStandardize(rect);
    size.width = size.width < 0 ? -size.width : size.width;
    size.height = size.height < 0 ? -size.height : size.height;
    CGPoint center = CGPointMake(CGRectGetMidX(rect), CGRectGetMidY(rect));
    switch (mode) {
        case UIViewContentModeScaleAspectFit:
        case UIViewContentModeScaleAspectFill: {
            if (rect.size.width < 0.01 || rect.size.height < 0.01 ||
                size.width < 0.01 || size.height < 0.01) {
                rect.origin = center;
                rect.size = CGSizeZero;
            } else {
                CGFloat scale;
                if (mode == UIViewContentModeScaleAspectFit) {
                    if (size.width / size.height < rect.size.width / rect.size.height) {
                        scale = rect.size.height / size.height;
                    } else {
                        scale = rect.size.width / size.width;
                    }
                } else {
                    if (size.width / size.height < rect.size.width / rect.size.height) {
                        scale = rect.size.width / size.width;
                    } else {
                        scale = rect.size.height / size.height;
                    }
                }
                size.width *= scale;
                size.height *= scale;
                rect.size = size;
                rect.origin = CGPointMake(center.x - size.width * 0.5, center.y - size.height * 0.5);
            }
        } break;
        case UIViewContentModeCenter: {
            rect.size = size;
            rect.origin = CGPointMake(center.x - size.width * 0.5, center.y - size.height * 0.5);
        } break;
        case UIViewContentModeTop: {
            rect.origin.x = center.x - size.width * 0.5;
            rect.size = size;
        } break;
        case UIViewContentModeBottom: {
            rect.origin.x = center.x - size.width * 0.5;
            rect.origin.y += rect.size.height - size.height;
            rect.size = size;
        } break;
        case UIViewContentModeLeft: {
            rect.origin.y = center.y - size.height * 0.5;
            rect.size = size;
        } break;
        case UIViewContentModeRight: {
            rect.origin.y = center.y - size.height * 0.5;
            rect.origin.x += rect.size.width - size.width;
            rect.size = size;
        } break;
        case UIViewContentModeTopLeft: {
            rect.size = size;
        } break;
        case UIViewContentModeTopRight: {
            rect.origin.x += rect.size.width - size.width;
            rect.size = size;
        } break;
        case UIViewContentModeBottomLeft: {
            rect.origin.y += rect.size.height - size.height;
            rect.size = size;
        } break;
        case UIViewContentModeBottomRight: {
            rect.origin.x += rect.size.width - size.width;
            rect.origin.y += rect.size.height - size.height;
            rect.size = size;
        } break;
        case UIViewContentModeScaleToFill:
        case UIViewContentModeRedraw:
        default: {
            rect = rect;
        }
    }
    return rect;
}

2. - (nullable UIImage *)imageByResizeToSize:(CGSize)size;

该方法的作用就是将原图像进行缩放，图像会根据需要进行延展。

方法实现

- (UIImage *)imageByResizeToSize:(CGSize)size {
    if (size.width <= 0 || size.height <= 0) return nil;
    UIGraphicsBeginImageContextWithOptions(size, NO, self.scale);
    [self drawInRect:CGRectMake(0, 0, size.width, size.height)];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

3. - (nullable UIImage *)imageByResizeToSize:(CGSize)size contentMode:(UIViewContentMode)contentMode;

该方法的作用就是将原图像进行缩放，这里会根据指定的contentMode进行缩放。

方法实现

- (UIImage *)imageByResizeToSize:(CGSize)size contentMode:(UIViewContentMode)contentMode {
    if (size.width <= 0 || size.height <= 0) return nil;
    UIGraphicsBeginImageContextWithOptions(size, NO, self.scale);
    [self drawInRect:CGRectMake(0, 0, size.width, size.height) withContentMode:contentMode clipsToBounds:NO];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

- (void)drawInRect:(CGRect)rect withContentMode:(UIViewContentMode)contentMode clipsToBounds:(BOOL)clips{
    CGRect drawRect = YYCGRectFitWithContentMode(rect, self.size, contentMode);
    if (drawRect.size.width == 0 || drawRect.size.height == 0) return;
    if (clips) {
        CGContextRef context = UIGraphicsGetCurrentContext();
        if (context) {
            CGContextSaveGState(context);
            CGContextAddRect(context, rect);
            CGContextClip(context);
            [self drawInRect:drawRect];
            CGContextRestoreGState(context);
        }
    } else {
        [self drawInRect:drawRect];
    }
}

4. - (nullable UIImage *)imageByCropToRect:(CGRect)rect;

该方法的作用就是对图像进行指定大小区域的裁剪。

方法实现

- (UIImage *)imageByCropToRect:(CGRect)rect {
    rect.origin.x *= self.scale;
    rect.origin.y *= self.scale;
    rect.size.width *= self.scale;
    rect.size.height *= self.scale;
    if (rect.size.width <= 0 || rect.size.height <= 0) return nil;
    CGImageRef imageRef = CGImageCreateWithImageInRect(self.CGImage, rect);
    UIImage *image = [UIImage imageWithCGImage:imageRef scale:self.scale orientation:self.imageOrientation];
    CGImageRelease(imageRef);
    return image;
}

5. - (nullable UIImage *)imageByInsetEdge:(UIEdgeInsets)insets withColor:(nullable UIColor *)color;

该方法的作用就是返回一个图像，该图像是在原图像的基础上缩进或者外扩一定的边距的结果。这里看一下两个参数：

• insets：边距，向内为正，向外为负
• color：边界的填充颜色，如果是nil就是clear color。

方法实现

- (UIImage *)imageByInsetEdge:(UIEdgeInsets)insets withColor:(UIColor *)color {
    CGSize size = self.size;
    size.width -= insets.left + insets.right;
    size.height -= insets.top + insets.bottom;
    if (size.width <= 0 || size.height <= 0) return nil;
    CGRect rect = CGRectMake(-insets.left, -insets.top, self.size.width, self.size.height);
    UIGraphicsBeginImageContextWithOptions(size, NO, self.scale);
    CGContextRef context = UIGraphicsGetCurrentContext();
    if (color) {
        CGContextSetFillColorWithColor(context, color.CGColor);
        CGMutablePathRef path = CGPathCreateMutable();
        CGPathAddRect(path, NULL, CGRectMake(0, 0, size.width, size.height));
        CGPathAddRect(path, NULL, rect);
        CGContextAddPath(context, path);
        CGContextEOFillPath(context);
        CGPathRelease(path);
    }
    [self drawInRect:rect];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

6. - (nullable UIImage *)imageByRoundCornerRadius:(CGFloat)radius;

该方法的作用就是带一定圆角的图像。

• radius：每个角落椭圆的半径。 大于矩形宽度或高度一半的值将被适当地限制为宽度或高度的一半。

方法实现

- (UIImage *)imageByRoundCornerRadius:(CGFloat)radius {
    return [self imageByRoundCornerRadius:radius borderWidth:0 borderColor:nil];
}

- (UIImage *)imageByRoundCornerRadius:(CGFloat)radius
                          borderWidth:(CGFloat)borderWidth
                          borderColor:(UIColor *)borderColor {
    return [self imageByRoundCornerRadius:radius
                                  corners:UIRectCornerAllCorners
                              borderWidth:borderWidth
                              borderColor:borderColor
                           borderLineJoin:kCGLineJoinMiter];
}

- (UIImage *)imageByRoundCornerRadius:(CGFloat)radius
                              corners:(UIRectCorner)corners
                          borderWidth:(CGFloat)borderWidth
                          borderColor:(UIColor *)borderColor
                       borderLineJoin:(CGLineJoin)borderLineJoin {
    
    if (corners != UIRectCornerAllCorners) {
        UIRectCorner tmp = 0;
        if (corners & UIRectCornerTopLeft) tmp |= UIRectCornerBottomLeft;
        if (corners & UIRectCornerTopRight) tmp |= UIRectCornerBottomRight;
        if (corners & UIRectCornerBottomLeft) tmp |= UIRectCornerTopLeft;
        if (corners & UIRectCornerBottomRight) tmp |= UIRectCornerTopRight;
        corners = tmp;
    }
    
    UIGraphicsBeginImageContextWithOptions(self.size, NO, self.scale);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
    CGContextScaleCTM(context, 1, -1);
    CGContextTranslateCTM(context, 0, -rect.size.height);
    
    CGFloat minSize = MIN(self.size.width, self.size.height);
    if (borderWidth < minSize / 2) {
        UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:CGRectInset(rect, borderWidth, borderWidth) byRoundingCorners:corners cornerRadii:CGSizeMake(radius, borderWidth)];
        [path closePath];
        
        CGContextSaveGState(context);
        [path addClip];
        CGContextDrawImage(context, rect, self.CGImage);
        CGContextRestoreGState(context);
    }
    
    if (borderColor && borderWidth < minSize / 2 && borderWidth > 0) {
        CGFloat strokeInset = (floor(borderWidth * self.scale) + 0.5) / self.scale;
        CGRect strokeRect = CGRectInset(rect, strokeInset, strokeInset);
        CGFloat strokeRadius = radius > self.scale / 2 ? radius - self.scale / 2 : 0;
        UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:strokeRect byRoundingCorners:corners cornerRadii:CGSizeMake(strokeRadius, borderWidth)];
        [path closePath];
        
        path.lineWidth = borderWidth;
        path.lineJoinStyle = borderLineJoin;
        [borderColor setStroke];
        [path stroke];
    }
    
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

7. - (nullable UIImage *)imageByRoundCornerRadius:(CGFloat)radius borderWidth:(CGFloat)borderWidth borderColor:(nullable UIColor *)borderColor;

该方法的作用就是获取指定圆角、边线宽度和边界颜色的图像。

• radius：圆角大小，大于矩形宽或者高的时候，被适当的限制为宽或者高的一半。
• borderWidth：内边线宽，大于矩形宽或者高的时候，被适当的限制为宽或者高的一半。
• borderColor：边线颜色，nil表示clear color

方法实现

- (UIImage *)imageByRoundCornerRadius:(CGFloat)radius
                          borderWidth:(CGFloat)borderWidth
                          borderColor:(UIColor *)borderColor {
    return [self imageByRoundCornerRadius:radius
                                  corners:UIRectCornerAllCorners
                              borderWidth:borderWidth
                              borderColor:borderColor
                           borderLineJoin:kCGLineJoinMiter];
}

- (UIImage *)imageByRoundCornerRadius:(CGFloat)radius
                              corners:(UIRectCorner)corners
                          borderWidth:(CGFloat)borderWidth
                          borderColor:(UIColor *)borderColor
                       borderLineJoin:(CGLineJoin)borderLineJoin {
    
    if (corners != UIRectCornerAllCorners) {
        UIRectCorner tmp = 0;
        if (corners & UIRectCornerTopLeft) tmp |= UIRectCornerBottomLeft;
        if (corners & UIRectCornerTopRight) tmp |= UIRectCornerBottomRight;
        if (corners & UIRectCornerBottomLeft) tmp |= UIRectCornerTopLeft;
        if (corners & UIRectCornerBottomRight) tmp |= UIRectCornerTopRight;
        corners = tmp;
    }
    
    UIGraphicsBeginImageContextWithOptions(self.size, NO, self.scale);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
    CGContextScaleCTM(context, 1, -1);
    CGContextTranslateCTM(context, 0, -rect.size.height);
    
    CGFloat minSize = MIN(self.size.width, self.size.height);
    if (borderWidth < minSize / 2) {
        UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:CGRectInset(rect, borderWidth, borderWidth) byRoundingCorners:corners cornerRadii:CGSizeMake(radius, borderWidth)];
        [path closePath];
        
        CGContextSaveGState(context);
        [path addClip];
        CGContextDrawImage(context, rect, self.CGImage);
        CGContextRestoreGState(context);
    }
    
    if (borderColor && borderWidth < minSize / 2 && borderWidth > 0) {
        CGFloat strokeInset = (floor(borderWidth * self.scale) + 0.5) / self.scale;
        CGRect strokeRect = CGRectInset(rect, strokeInset, strokeInset);
        CGFloat strokeRadius = radius > self.scale / 2 ? radius - self.scale / 2 : 0;
        UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:strokeRect byRoundingCorners:corners cornerRadii:CGSizeMake(strokeRadius, borderWidth)];
        [path closePath];
        
        path.lineWidth = borderWidth;
        path.lineJoinStyle = borderLineJoin;
        [borderColor setStroke];
        [path stroke];
    }
    
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

8. - (nullable UIImage *)imageByRoundCornerRadius:(CGFloat)radius corners:(UIRectCorner)corners borderWidth:(CGFloat)borderWidth borderColor:(nullable UIColor *)borderColor borderLineJoin:(CGLineJoin)borderLineJoin;

该方法的作用就是获取指定圆角、线宽、线色以及连接类型的图像。

方法实现

- (UIImage *)imageByRoundCornerRadius:(CGFloat)radius
                              corners:(UIRectCorner)corners
                          borderWidth:(CGFloat)borderWidth
                          borderColor:(UIColor *)borderColor
                       borderLineJoin:(CGLineJoin)borderLineJoin {
    
    if (corners != UIRectCornerAllCorners) {
        UIRectCorner tmp = 0;
        if (corners & UIRectCornerTopLeft) tmp |= UIRectCornerBottomLeft;
        if (corners & UIRectCornerTopRight) tmp |= UIRectCornerBottomRight;
        if (corners & UIRectCornerBottomLeft) tmp |= UIRectCornerTopLeft;
        if (corners & UIRectCornerBottomRight) tmp |= UIRectCornerTopRight;
        corners = tmp;
    }
    
    UIGraphicsBeginImageContextWithOptions(self.size, NO, self.scale);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
    CGContextScaleCTM(context, 1, -1);
    CGContextTranslateCTM(context, 0, -rect.size.height);
    
    CGFloat minSize = MIN(self.size.width, self.size.height);
    if (borderWidth < minSize / 2) {
        UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:CGRectInset(rect, borderWidth, borderWidth) byRoundingCorners:corners cornerRadii:CGSizeMake(radius, borderWidth)];
        [path closePath];
        
        CGContextSaveGState(context);
        [path addClip];
        CGContextDrawImage(context, rect, self.CGImage);
        CGContextRestoreGState(context);
    }
    
    if (borderColor && borderWidth < minSize / 2 && borderWidth > 0) {
        CGFloat strokeInset = (floor(borderWidth * self.scale) + 0.5) / self.scale;
        CGRect strokeRect = CGRectInset(rect, strokeInset, strokeInset);
        CGFloat strokeRadius = radius > self.scale / 2 ? radius - self.scale / 2 : 0;
        UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:strokeRect byRoundingCorners:corners cornerRadii:CGSizeMake(strokeRadius, borderWidth)];
        [path closePath];
        
        path.lineWidth = borderWidth;
        path.lineJoinStyle = borderLineJoin;
        [borderColor setStroke];
        [path stroke];
    }
    
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

9. - (nullable UIImage *)imageByRotate:(CGFloat)radians fitSize:(BOOL)fitSize;

该方法的作用就是返回一个旋转的图像。

• radians：逆时针旋转弧度
• fitSize：YES：新图片的大小被扩展到适合所有内容。 NO：图片的大小不会改变，内容可能会被剪裁。

方法实现

- (UIImage *)imageByRotate:(CGFloat)radians fitSize:(BOOL)fitSize {
    size_t width = (size_t)CGImageGetWidth(self.CGImage);
    size_t height = (size_t)CGImageGetHeight(self.CGImage);
    CGRect newRect = CGRectApplyAffineTransform(CGRectMake(0., 0., width, height),
                                                fitSize ? CGAffineTransformMakeRotation(radians) : CGAffineTransformIdentity);
    
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(NULL,
                                                 (size_t)newRect.size.width,
                                                 (size_t)newRect.size.height,
                                                 8,
                                                 (size_t)newRect.size.width * 4,
                                                 colorSpace,
                                                 kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedFirst);
    CGColorSpaceRelease(colorSpace);
    if (!context) return nil;
    
    CGContextSetShouldAntialias(context, true);
    CGContextSetAllowsAntialiasing(context, true);
    CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
    
    CGContextTranslateCTM(context, +(newRect.size.width * 0.5), +(newRect.size.height * 0.5));
    CGContextRotateCTM(context, radians);
    
    CGContextDrawImage(context, CGRectMake(-(width * 0.5), -(height * 0.5), width, height), self.CGImage);
    CGImageRef imgRef = CGBitmapContextCreateImage(context);
    UIImage *img = [UIImage imageWithCGImage:imgRef scale:self.scale orientation:self.imageOrientation];
    CGImageRelease(imgRef);
    CGContextRelease(context);
    return img;
}

10. - (nullable UIImage *)imageByRotateLeft90;

该方法的作用就是逆时针旋转90度，图像的宽高将会交换。

方法实现

- (UIImage *)imageByRotateLeft90 {
    return [self imageByRotate:DegreesToRadians(90) fitSize:YES];
}

/// Convert degrees to radians.
static inline CGFloat DegreesToRadians(CGFloat degrees) {
    return degrees * M_PI / 180;
}

- (UIImage *)imageByRotate:(CGFloat)radians fitSize:(BOOL)fitSize {
    size_t width = (size_t)CGImageGetWidth(self.CGImage);
    size_t height = (size_t)CGImageGetHeight(self.CGImage);
    CGRect newRect = CGRectApplyAffineTransform(CGRectMake(0., 0., width, height),
                                                fitSize ? CGAffineTransformMakeRotation(radians) : CGAffineTransformIdentity);
    
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(NULL,
                                                 (size_t)newRect.size.width,
                                                 (size_t)newRect.size.height,
                                                 8,
                                                 (size_t)newRect.size.width * 4,
                                                 colorSpace,
                                                 kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedFirst);
    CGColorSpaceRelease(colorSpace);
    if (!context) return nil;
    
    CGContextSetShouldAntialias(context, true);
    CGContextSetAllowsAntialiasing(context, true);
    CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
    
    CGContextTranslateCTM(context, +(newRect.size.width * 0.5), +(newRect.size.height * 0.5));
    CGContextRotateCTM(context, radians);
    
    CGContextDrawImage(context, CGRectMake(-(width * 0.5), -(height * 0.5), width, height), self.CGImage);
    CGImageRef imgRef = CGBitmapContextCreateImage(context);
    UIImage *img = [UIImage imageWithCGImage:imgRef scale:self.scale orientation:self.imageOrientation];
    CGImageRelease(imgRef);
    CGContextRelease(context);
    return img;
}

11. - (nullable UIImage *)imageByRotateRight90;

该方法的作用就是右旋转90度，图像的宽高将会交换。

方法实现

- (UIImage *)imageByRotateRight90 {
    return [self imageByRotate:DegreesToRadians(-90) fitSize:YES];
}

这个方法的实现，和上面向左旋转是一样的，不同的就是在于弧度和度的转化上的区别。

12. - (nullable UIImage *)imageByRotate180;

该方法的作用就是返回旋转180度后的图像，↻。

方法实现

- (UIImage *)imageByRotate180 {
    return [self _yy_flipHorizontal:YES vertical:YES];
}

- (UIImage *)_yy_flipHorizontal:(BOOL)horizontal vertical:(BOOL)vertical {
    if (!self.CGImage) return nil;
    size_t width = (size_t)CGImageGetWidth(self.CGImage);
    size_t height = (size_t)CGImageGetHeight(self.CGImage);
    size_t bytesPerRow = width * 4;
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(NULL, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedFirst);
    CGColorSpaceRelease(colorSpace);
    if (!context) return nil;
    
    CGContextDrawImage(context, CGRectMake(0, 0, width, height), self.CGImage);
    UInt8 *data = (UInt8 *)CGBitmapContextGetData(context);
    if (!data) {
        CGContextRelease(context);
        return nil;
    }
    vImage_Buffer src = { data, height, width, bytesPerRow };
    vImage_Buffer dest = { data, height, width, bytesPerRow };
    if (vertical) {
        vImageVerticalReflect_ARGB8888(&src, &dest, kvImageBackgroundColorFill);
    }
    if (horizontal) {
        vImageHorizontalReflect_ARGB8888(&src, &dest, kvImageBackgroundColorFill);
    }
    CGImageRef imgRef = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    UIImage *img = [UIImage imageWithCGImage:imgRef scale:self.scale orientation:self.imageOrientation];
    CGImageRelease(imgRef);
    return img;
}

13. - (nullable UIImage *)imageByFlipVertical;

该方法的作用就是返回垂直翻转后的图像，⥯。

方法实现

- (UIImage *)imageByFlipVertical {
    return [self _yy_flipHorizontal:NO vertical:YES];
}

这里调用的方法就是上面的那个方法，不同的是传入参数YES和NO的区别，这是垂直翻转所以vertical为YES。

14. - (nullable UIImage *)imageByFlipHorizontal;

该方法的作用就是返回水平翻转后的图像，⇋。

方法实现

- (UIImage *)imageByFlipHorizontal {
    return [self _yy_flipHorizontal:YES vertical:NO];
}

后记

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