iOS UIImage扩展方法(category):放大、旋转、合并UIImage、增加渐变层、添加阴影、调节透明度、保存到相册

一有用的 UIImage 扩展，支持（等比例）放大和旋转可在许多 App 中使用。

UIImage-Extensions.h

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h> 
CGFloat DegreesToRadians(CGFloat degrees);

CGFloat RadiansToDegrees(CGFloat radians);

@interface UIImage (JQ_Extensions)
- (UIImage *)imageAtRect:(CGRect)rect;- (UIImage *)imageByScalingProportionallyToSize:(CGSize)targetSize;
- (UIImage *)imageByScalingToSize:(CGSize)targetSize;
- (UIImage *)imageRotatedByRadians:(CGFloat)radians;
- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees;

- (UIImage *)addImage:(UIImage *)image1 toImage:(UIImage *)image2;
[objc] view plaincopyprint?
- (UIImage *) imageWithBackgroundColor:(UIColor *)bgColor  
                           shadeAlpha1:(CGFloat)alpha1  
                           shadeAlpha2:(CGFloat)alpha2  
                           shadeAlpha3:(CGFloat)alpha3  
                           shadowColor:(UIColor *)shadowColor  
                          shadowOffset:(CGSize)shadowOffset  
                            shadowBlur:(CGFloat)shadowBlur;  
- (UIImage *)imageWithShadowColor:(UIColor *)shadowColor  
                     shadowOffset:(CGSize)shadowOffset  
                       shadowBlur:(CGFloat)shadowBlur;<br>  
- (UIImage *)imageByApplyingAlpha:(CGFloat)alpha;  
  -  ( void ) saveToAlbumWithMetadata: ( NSDictionary  * ) metadata
 customAlbumName: ( NSString  * ) customAlbumName
 completionBlock: ( void  ( ^ )( void )) completionBlock
     failureBlock: ( void  ( ^ )( NSError  * error )) failureBlock
@end;
UIImage-Extensions.m

#import "UIImage-Extensions.h"

CGFloat DegreesToRadians(CGFloat degrees) {return degrees * M_PI / 180;};
CGFloat RadiansToDegrees(CGFloat radians) {return radians * 180/M_PI;};

@implementation UIImage (JQ_Extensions)

-(UIImage *)imageAtRect:(CGRect)rect
{
    
    CGImageRef imageRef = CGImageCreateWithImageInRect([self CGImage], rect);
    UIImage* subImage = [UIImage imageWithCGImage: imageRef];
    CGImageRelease(imageRef);
    
    return subImage;
    
}
- (UIImage *)imageByScalingProportionallyToSize:(CGSize)targetSize {
    
    UIImage *sourceImage = self;
    UIImage *newImage = nil;
    
    CGSize imageSize = sourceImage.size;
    CGFloat width = imageSize.width;
    CGFloat height = imageSize.height;
    
    CGFloat targetWidth = targetSize.width;
    CGFloat targetHeight = targetSize.height;
    
    CGFloat scaleFactor = 0.0;
    CGFloat scaledWidth = targetWidth;
    CGFloat scaledHeight = targetHeight;
    
    CGPoint thumbnailPoint = CGPointMake(0.0,0.0);
    
    if (CGSizeEqualToSize(imageSize, targetSize) == NO) {
        
        CGFloat widthFactor = targetWidth / width;
        CGFloat heightFactor = targetHeight / height;
        
        if (widthFactor < heightFactor) 
            scaleFactor = widthFactor;
        else
            scaleFactor = heightFactor;
        
        scaledWidth  = width * scaleFactor;
        scaledHeight = height * scaleFactor;
        
        // center the image
        
        if (widthFactor < heightFactor) {
            thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5; 
        } else if (widthFactor > heightFactor) {
            thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
        }
    }
    
    
    // this is actually the interesting part:
    
    UIGraphicsBeginImageContext(targetSize);
    
    CGRect thumbnailRect = CGRectZero;
    thumbnailRect.origin = thumbnailPoint;
    thumbnailRect.size.width  = scaledWidth;
    thumbnailRect.size.height = scaledHeight;
    
    [sourceImage drawInRect:thumbnailRect];
    
    newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    if(newImage == nil) NSLog(@"could not scale image");
    
    
    return newImage ;
}


- (UIImage *)imageByScalingToSize:(CGSize)targetSize {
    
    UIImage *sourceImage = self;
    UIImage *newImage = nil;
    
    //   CGSize imageSize = sourceImage.size;
    //   CGFloat width = imageSize.width;
    //   CGFloat height = imageSize.height;
    
    CGFloat targetWidth = targetSize.width;
    CGFloat targetHeight = targetSize.height;
    
    //   CGFloat scaleFactor = 0.0;
    CGFloat scaledWidth = targetWidth;
    CGFloat scaledHeight = targetHeight;
    
    CGPoint thumbnailPoint = CGPointMake(0.0,0.0);
    
    // this is actually the interesting part:
    
    UIGraphicsBeginImageContext(targetSize);
    
    CGRect thumbnailRect = CGRectZero;
    thumbnailRect.origin = thumbnailPoint;
    thumbnailRect.size.width  = scaledWidth;
    thumbnailRect.size.height = scaledHeight;
    
    [sourceImage drawInRect:thumbnailRect];
    
    newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    if(newImage == nil) NSLog(@"could not scale image");
    
    
    return newImage ;
}


- (UIImage *)imageRotatedByRadians:(CGFloat)radians
{
    return [self imageRotatedByDegrees:RadiansToDegrees(radians)];
}

- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees 
{   
    // calculate the size of the rotated view's containing box for our drawing space
    UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,self.size.width, self.size.height)];
    CGAffineTransform t = CGAffineTransformMakeRotation(DegreesToRadians(degrees));
    rotatedViewBox.transform = t;
    CGSize rotatedSize = rotatedViewBox.frame.size;
    [rotatedViewBox release];
    
    // Create the bitmap context
    UIGraphicsBeginImageContext(rotatedSize);
    CGContextRef bitmap = UIGraphicsGetCurrentContext();
    
    // Move the origin to the middle of the image so we will rotate and scale around the center.
    CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);
    
    //   // Rotate the image context
    CGContextRotateCTM(bitmap, DegreesToRadians(degrees));
    
    // Now, draw the rotated/scaled image into the context
    CGContextScaleCTM(bitmap, 1.0, -1.0);
    CGContextDrawImage(bitmap, CGRectMake(-self.size.width / 2, -self.size.height / 2, self.size.width, self.size.height), [self CGImage]);
    
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
    
}

// Combine two UIImages

[objc] view plaincopyprint?
- (UIImage *)addImage:(UIImage *)image1 toImage:(UIImage *)image2 {  
    UIGraphicsBeginImageContext(image2.size);  
      
    // Draw image1  
    [image1 drawInRect:CGRectMake(0, 0, image1.size.width, image1.size.height)];  
      
    // Draw image2  
    [image2 drawInRect:CGRectMake(0, 0, image2.size.width, image2.size.height)];  
      
    UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();  
    UIGraphicsEndImageContext();<br>  
    return resultingImage;  
}  
[objc] view plaincopyprint?
- (UIImage *) imageWithBackgroundColor:(UIColor *)bgColor  
                           shadeAlpha1:(CGFloat)alpha1  
                           shadeAlpha2:(CGFloat)alpha2  
                           shadeAlpha3:(CGFloat)alpha3  
                           shadowColor:(UIColor *)shadowColor  
                          shadowOffset:(CGSize)shadowOffset  
                            shadowBlur:(CGFloat)shadowBlur {  
    UIImage *image = self;  
    CGColorRef cgColor = [bgColor CGColor];  
    CGColorRef cgShadowColor = [shadowColor CGColor];  
    CGFloat components[16] = {1,1,1,alpha1,1,1,1,alpha1,1,1,1,alpha2,1,1,1,alpha3};  
    CGFloat locations[4] = {0,0.5,0.6,1};  
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();  
    CGGradientRef colorGradient = CGGradientCreateWithColorComponents(colorSpace, components, locations, (size_t)4);  
    CGRect contextRect;  
    contextRect.origin.x = 0.0f;  
    contextRect.origin.y = 0.0f;  
    contextRect.size = [image size];  
    //contextRect.size = CGSizeMake([image size].width+5,[image size].height+5);  
    // Retrieve source image and begin image context  
    UIImage *itemImage = image;  
    CGSize itemImageSize = [itemImage size];  
    CGPoint itemImagePosition;  
    itemImagePosition.x = ceilf((contextRect.size.width - itemImageSize.width) / 2);  
    itemImagePosition.y = ceilf((contextRect.size.height - itemImageSize.height) / 2);  
    UIGraphicsBeginImageContext(contextRect.size);  
    CGContextRef c = UIGraphicsGetCurrentContext();  
    // Setup shadow  
    CGContextSetShadowWithColor(c, shadowOffset, shadowBlur, cgShadowColor);  
    // Setup transparency layer and clip to mask  
    CGContextBeginTransparencyLayer(c, NULL);  
    CGContextScaleCTM(c, 1.0, -1.0);  
    CGContextClipToMask(c, CGRectMake(itemImagePosition.x, -itemImagePosition.y, itemImageSize.width, -itemImageSize.height), [itemImage CGImage]);  
    // Fill and end the transparency layer  
    CGContextSetFillColorWithColor(c, cgColor);  
    contextRect.size.height = -contextRect.size.height;  
    CGContextFillRect(c, contextRect);  
    CGContextDrawLinearGradient(c, colorGradient,CGPointZero,CGPointMake(contextRect.size.width*1.0/4.0,contextRect.size.height),0);  
    CGContextEndTransparencyLayer(c);  
    //CGPointMake(contextRect.size.width*3.0/4.0, 0)  
    // Set selected image and end context  
    UIImage *resultImage = UIGraphicsGetImageFromCurrentImageContext();  
    UIGraphicsEndImageContext();  
    CGColorSpaceRelease(colorSpace);  
    CGGradientRelease(colorGradient);  
    return resultImage;  
}  
  
- (UIImage *)imageWithShadowColor:(UIColor *)shadowColor  
                     shadowOffset:(CGSize)shadowOffset  
                       shadowBlur:(CGFloat)shadowBlur  
{  
    CGColorRef cgShadowColor = [shadowColor CGColor];  
    CGColorSpaceRef colourSpace = CGColorSpaceCreateDeviceRGB();  
    CGContextRef shadowContext = CGBitmapContextCreate(NULL, self.size.width, self.size.height,  
                                                       CGImageGetBitsPerComponent(self.CGImage), 0,  
                                                       colourSpace, kCGImageAlphaPremultipliedLast);  
    CGColorSpaceRelease(colourSpace);  
      
    // Setup shadow  
    CGContextSetShadowWithColor(shadowContext, shadowOffset, shadowBlur, cgShadowColor);  
    CGRect drawRect = CGRectMake(-shadowBlur, -shadowBlur, self.size.width + shadowBlur, self.size.height + shadowBlur);  
    CGContextDrawImage(shadowContext, drawRect, self.CGImage);  
      
    CGImageRef shadowedCGImage = CGBitmapContextCreateImage(shadowContext);  
    CGContextRelease(shadowContext);  
      
    UIImage * shadowedImage = [UIImage imageWithCGImage:shadowedCGImage];  
    CGImageRelease(shadowedCGImage);  
      
    return shadowedImage;  
}  
  
- (UIImage *)imageByApplyingAlpha:(CGFloat)alpha {  
    UIGraphicsBeginImageContextWithOptions(self.size, NO, 0.0f);  
      
    CGContextRef ctx = UIGraphicsGetCurrentContext();  
    CGRect area = CGRectMake(0, 0, self.size.width, self.size.height);  
      
    CGContextScaleCTM(ctx, 1, -1);  
    CGContextTranslateCTM(ctx, 0, -area.size.height);  
      
    CGContextSetBlendMode(ctx, kCGBlendModeMultiply);  
      
    CGContextSetAlpha(ctx, alpha);  
      
    CGContextDrawImage(ctx, area, self.CGImage);  
      
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();  
      
    UIGraphicsEndImageContext();  
      
    return newImage;  
}  

- ( void ) saveToAlbumWithMetadata: ( NSDictionary * ) metadata
                 customAlbumName: ( NSString * ) customAlbumName
                 completionBlock: ( void ( ^ )( void )) completionBlock
                    failureBlock: ( void ( ^ )( NSError * error )) failureBlock
{
     NSData * imageData = UIImagePNGRepresentation ( self );
     ALAssetsLibrary * assetsLibrary = [[ ALAssetsLibrary alloc ] init ];
     void ( ^ AddAsset )( ALAssetsLibrary * , NSURL * ) = ^ ( ALAssetsLibrary * assetsLibrary , NSURL * assetURL ) {
         [ assetsLibrary assetForURL : assetURL resultBlock :^ ( ALAsset * asset ) {
             [ assetsLibrary enumerateGroupsWithTypes : ALAssetsGroupAll usingBlock :^ ( ALAssetsGroup * group , BOOL * stop ) {
                 if ([[ group valueForProperty : ALAssetsGroupPropertyName ] isEqualToString : customAlbumName ]) {
                     [ group addAsset : asset ];
                     if ( completionBlock ) {
                         completionBlock ();
                     }
                 }
             } failureBlock :^ ( NSError * error ) {
                 if ( failureBlock ) {
                     failureBlock ( error );
                 }
             }];
         } failureBlock :^ ( NSError * error ) {
             if ( failureBlock ) {
                 failureBlock ( error );
             }
         }];
     };
     [ assetsLibrary writeImageDataToSavedPhotosAlbum : imageData metadata : metadata completionBlock :^ ( NSURL * assetURL , NSError * error ) {
         if ( customAlbumName ) {
             [ assetsLibrary addAssetsGroupAlbumWithName : customAlbumName resultBlock :^ ( ALAssetsGroup * group ) {
                 if ( group ) {
                     [ assetsLibrary assetForURL : assetURL resultBlock :^ ( ALAsset * asset ) {
                         [ group addAsset : asset ];
                         if ( completionBlock ) {
                             completionBlock ();
                         }
                     } failureBlock :^ ( NSError * error ) {
                         if ( failureBlock ) {
                             failureBlock ( error );
                         }
                     }];
                 } else {
                     AddAsset ( assetsLibrary , assetURL );
                 }
             } failureBlock :^ ( NSError * error ) {
                 AddAsset ( assetsLibrary , assetURL );
             }];
         } else {
             if ( completionBlock ) {
                 completionBlock ();
             }
         }
     }];
}
@end;