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;
- (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;
- (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
- (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();
return resultingImage;
}
- (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;
