iOS中大尺寸图片的旋转与缩放实例详解

+ (UIImage *)image:(UIImage *)image rotation:(UIImageOrientation)orientation {

 long double rotate = 0.0;
 CGRect rect;
 float translateX = 0;
 float translateY = 0;
 float scaleX = 1.0;
 float scaleY = 1.0;

 switch (orientation) {
 case UIImageOrientationLeft:
 rotate = M_PI_2;
 rect = CGRectMake(0, 0, image.size.height, image.size.width);
 translateX = 0;
 translateY = -rect.size.width;
 scaleY = rect.size.width/rect.size.height;
 scaleX = rect.size.height/rect.size.width;
 break;
 default:
 rotate = 0.0;
 rect = CGRectMake(0, 0, image.size.width, image.size.height);
 translateX = 0;
 translateY = 0;
 break;
 }

 UIGraphicsBeginImageContext(rect.size);
 CGContextRef cOntext= UIGraphicsGetCurrentContext();
 //做CTM变换
 CGContextTranslateCTM(context, 0.0, rect.size.height);
 CGContextScaleCTM(context, 1.0, -1.0);
 CGContextRotateCTM(context, rotate);
 CGContextTranslateCTM(context, translateX, translateY);

 CGContextScaleCTM(context, scaleX, scaleY);
 //绘制图片
 CGContextDrawImage(context, CGRectMake(0, 0, rect.size.width, rect.size.height), image.CGImage);
 UIImage *newPic = UIGraphicsGetImageFromCurrentImageContext();
 return newPic;
} 

+ (UIImage *)getRotationImage:(UIImage *)image rotation:(CGFloat)rotation {

 CIImage *ciImage = [[CIImage alloc] initWithImage:image];
 CIFilter *filter = [CIFilter filterWithName:@"CIAffineTransform" keysAndValues:kCIInputImageKey, ciImage, nil];

 [filter setDefaults];
 CGAffineTransform transform = CATransform3DGetAffineTransform([self rotateTransform:CATransform3DIdentity clockwise:NO angle:rotation]);
 [filter setValue:[NSValue valueWithBytes:&transform objCType:@encode(CGAffineTransform)] forKey:@"inputTransform"];

 //根据滤镜设置图片
 CIContext *cOntext= [CIContext contextWithOptions:@{kCIContextUseSoftwareRenderer : @(NO)}];
 CIImage *outputImage = [filter outputImage];
 CGImageRef cgImage = [context createCGImage:outputImage fromRect:[outputImage extent]];

 UIImage *result = [UIImage imageWithCGImage:cgImage];

 CGImageRelease(cgImage);

 return result;
}
+ (CATransform3D)rotateTransform:(CATransform3D)initialTransform clockwise:(BOOL)clockwise angle:(CGFloat)angle {

 CGFloat arg = angle*M_PI / 180.0f;
 if(!clockwise){
 arg *= -1;
 }
 //进行形变
 CATransform3D transform = initialTransform;
 transform = CATransform3DRotate(transform, arg, 0, 0, 1);
 CGFloat _flipState1 = 0;
 CGFloat _flipState2 = 0;
 transform = CATransform3DRotate(transform, _flipState1*M_PI, 0, 1, 0);
 transform = CATransform3DRotate(transform, _flipState2*M_PI, 1, 0, 0);

 return transform;
} 

+ (UIImage *)image:(UIImage *)image transformtoSize:(CGSize)Newsize {
 // 创建一个bitmap的context
 UIGraphicsBeginImageContext(Newsize);
 // 绘制改变大小的图片
 [image drawInRect:CGRectMake(0, 0, Newsize.width, Newsize.height)];
 // 从当前context中创建一个改变大小后的图片
 UIImage *TransformedImg=UIGraphicsGetImageFromCurrentImageContext();
 // 使当前的context出堆栈
 UIGraphicsEndImageContext();
 // 返回新的改变大小后的图片
 return TransformedImg;
}

+(UIImage *)resizeImage:(UIImage *)image toSize:(CGSize)size {

 CIImage *ciImage = [[CIImage alloc] initWithImage:image];
 //创建一个input image类型的滤镜
 CIFilter *filter = [CIFilter filterWithName:@"CIAffineTransform" keysAndValues:kCIInputImageKey, ciImage, nil];
 //设置默认的滤镜效果
 [filter setDefaults];

 //设置缩放比例
 CGFloat scale = 1;
 if (size.width != CGFLOAT_MAX) {
 scale = (CGFloat) size.width / image.size.width;
 } else if (size.height != CGFLOAT_MAX) {
 scale = (CGFloat) size.height / image.size.height;
 }

 //进行赋值
 CGAffineTransform transform = CGAffineTransformMakeScale(scale, scale);
 [filter setValue:[NSValue valueWithBytes:&transform objCType:@encode(CGAffineTransform)] forKey:@"inputTransform"];

 //通过GPU的方式来进行处理
 CIContext *cOntext= [CIContext contextWithOptions:@{kCIContextUseSoftwareRenderer : @(NO)}];
 //根据滤镜输出图片
 CIImage *outputImage = [filter outputImage];
 CGImageRef cgImage = [context createCGImage:outputImage fromRect:[outputImage extent]];
 //创建UIImage 对象，并释放资源
 UIImage *result = [UIImage imageWithCGImage:cgImage];

 CGImageRelease(cgImage);

 return result;
}