自由手記

0. -(UIImage *)getImageFromImage{
0.     //大图bigImage
0.     //定义myImageRect，截图的区域
0.     CGRect myImageRect = CGRectMake(10.0, 10.0, 57.0, 57.0);
0.     UIImage* bigImage= [UIImage imageNamed:@"k00030.jpg"];
0.     CGImageRef imageRef = bigImage.CGImage;
0.     CGImageRef subImageRef = CGImageCreateWithImageInRect(imageRef, myImageRect);
0.     CGSize size;
0.     size.width = 57.0;
0.     size.height = 57.0;
0.     UIGraphicsBeginImageContext(size);
0.     CGContextRef context = UIGraphicsGetCurrentContext();
0.     CGContextDrawImage(context, myImageRect, subImageRef);
0.     UIImage* smallImage = [UIImage imageWithCGImage:subImageRef];
0.     UIGraphicsEndImageContext();
0.     return smallImage;
0. }

0. -(UIImage*)resizedImage1:(UIImage*)inImage  inRect:(CGRect)thumbRect {
0.     // Creates a bitmap-based graphics context and makes it the current context.
0.     UIGraphicsBeginImageContext(thumbRect.size);
0.     [inImage drawInRect:thumbRect];
0.     return UIGraphicsGetImageFromCurrentImageContext();
0. }
0. -(UIImage*)resizedImage2:(UIImage*)inImage  inRect:(CGRect)thumbRect {
0.     CGImageRef          imageRef = [inImage CGImage];
0.     CGImageAlphaInfo    alphaInfo = CGImageGetAlphaInfo(imageRef);
0.     /* There's a wierdness with kCGImageAlphaNone and CGBitmapContextCreate
0.     see Supported Pixel Formats in the Quartz 2D Programming Guide
0.     Creating a Bitmap Graphics Context section
0.     only RGB 8 bit images with alpha of kCGImageAlphaNoneSkipFirst,         kCGImageAlphaNoneSkipLast, kCGImageAlphaPremultipliedFirst,and kCGImageAlphaPremultipliedLast, with a few other oddball image kinds are supported
0. The images on input here are likely to be png or jpeg files*/
0.     if (alphaInfo == kCGImageAlphaNone)
0.         alphaInfo = kCGImageAlphaNoneSkipLast;
0.         // Build a bitmap context that's the size of the thumbRect
0.        CGFloat bytesPerRow;
0.     if( thumbRect.size.width > thumbRect.size.height ) {
0.        bytesPerRow = 4 * thumbRect.size.width;
0.     } else {
0.        bytesPerRow = 4 * thumbRect.size.height;
0.     }
0.     CGContextRef bitmap = CGBitmapContextCreate(NULL,
0.                                                         thumbRect.size.width,       // width
0.                                                         thumbRect.size.height,      // height
0.                                                         8, //CGImageGetBitsPerComponent(imageRef),  // really needs to always be 8
0.                                                         bytesPerRow, //4 * thumbRect.size.width,    // rowbytes
0.                                                         CGImageGetColorSpace(imageRef),
0.                                                         alphaInfo
0. );
0.     // Draw into the context, this scales the image
0.     CGContextDrawImage(bitmap, thumbRect, imageRef);
0.     // Get an image from the context and a UIImage
0.     CGImageRef  ref = CGBitmapContextCreateImage(bitmap);
0.     UIImage*    result = [UIImage imageWithCGImage:ref];
0.     CGContextRelease(bitmap);   // ok if NULL
0.     CGImageRelease(ref);
0.     return result;
0. }
0. - (UIImage *)scaleImage:(UIImage *) image maxWidth:(float) maxWidth maxHeight:(float) maxHeight
0. {
0.     CGImageRef imgRef = image.CGImage;
0.     CGFloat width = CGImageGetWidth(imgRef);
0.     CGFloat height = CGImageGetHeight(imgRef);
0.     if (width <= maxWidth && height <= maxHeight)
0.     {
0.         return image;
0.     }
0.     CGAffineTransform transform = CGAffineTransformIdentity;
0.     CGRect bounds = CGRectMake(0, 0, width, height);
0.     if (width > maxWidth || height > maxHeight)
0.     {
0.         CGFloat ratio = width/height;
0.         if (ratio > 1)
0.         {
0.             bounds.size.width = maxWidth;
0.             bounds.size.height = bounds.size.width / ratio;
0.         }
0.         else
0.         {
0.             bounds.size.height = maxHeight;
0.              bounds.size.width = bounds.size.height * ratio;
0.         }
0.     }
0.     CGFloat scaleRatio = bounds.size.width / width;
0.     UIGraphicsBeginImageContext(bounds.size);
0.     CGContextRef context = UIGraphicsGetCurrentContext();
0.     CGContextScaleCTM(context, scaleRatio, -scaleRatio);
0.     CGContextTranslateCTM(context, 0, -height);
0.     CGContextConcatCTM(context, transform);
0.     CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);
0.     UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
0.     UIGraphicsEndImageContext();
0.     return imageCopy;
0. }

0. -(UIImage*) scaleAndRotateImage:(UIImage*)photoimage:(CGFloat)bounds_width:(CGFloat)bounds_height
0. {
0.     //int kMaxResolution = 300;
0.     CGImageRef imgRef =photoimage.CGImage;
0.     CGFloat width = CGImageGetWidth(imgRef);
0.     CGFloat height = CGImageGetHeight(imgRef);
0.     CGAffineTransform transform = CGAffineTransformIdentity;
0.     CGRect bounds = CGRectMake(0, 0, width, height);
0.     /*if (width > kMaxResolution || height > kMaxResolution)
0.     {
0.         CGFloat ratio = width/height;
0.         if (ratio > 1)
0.         {
0.             bounds.size.width = kMaxResolution;
0.             bounds.size.height = bounds.size.width / ratio;
0.         }
0.         else
0.         {
0.             bounds.size.height = kMaxResolution;
0.             bounds.size.width = bounds.size.height * ratio;
0.         }
0.     }*/
0.     bounds.size.width = bounds_width;
0.     bounds.size.height = bounds_height;
0.     CGFloat scaleRatio = bounds.size.width / width;
0.     CGFloat scaleRatioheight = bounds.size.height / height;
0.     CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));
0.     CGFloat boundHeight;
0.     UIImageOrientation orient =photoimage.imageOrientation;
0.     switch(orient)
0.     {
0.         case UIImageOrientationUp: //EXIF = 1
0.             transform = CGAffineTransformIdentity;
0.             break;
0.         case UIImageOrientationUpMirrored: //EXIF = 2
0.             transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0);
0.             transform = CGAffineTransformScale(transform, -1.0, 1.0);
0.             break;
0.         case UIImageOrientationDown: //EXIF = 3
0.             transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height);
0.             transform = CGAffineTransformRotate(transform, M_PI);
0.             break;
0.         case UIImageOrientationDownMirrored: //EXIF = 4
0.             transform = CGAffineTransformMakeTranslation(0.0, imageSize.height);
0.             transform = CGAffineTransformScale(transform, 1.0, -1.0);
0.             break;
0.         case UIImageOrientationLeftMirrored: //EXIF = 5
0.             boundHeight = bounds.size.height;
0.             bounds.size.height = bounds.size.width;
0.             bounds.size.width = boundHeight;
0.             transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width);
0.             transform = CGAffineTransformScale(transform, -1.0, 1.0);
0.             transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
0.             break;
0.         case UIImageOrientationLeft: //EXIF = 6
0.             boundHeight = bounds.size.height;
0.             bounds.size.height = bounds.size.width;
0.             bounds.size.width = boundHeight;
0.             transform = CGAffineTransformMakeTranslation(0.0, imageSize.width);
0.             transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
0.             break;
0.         case UIImageOrientationRightMirrored: //EXIF = 7
0.             boundHeight = bounds.size.height;
0.             bounds.size.height = bounds.size.width;
0.             bounds.size.width = boundHeight;
0.             transform = CGAffineTransformMakeScale(-1.0, 1.0);
0.             transform = CGAffineTransformRotate(transform, M_PI / 2.0);
0.             break;
0.         case UIImageOrientationRight: //EXIF = 8
0.             boundHeight = bounds.size.height;
0.             bounds.size.height = bounds.size.width;
0.             bounds.size.width = boundHeight;
0.             transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0);
0.             transform = CGAffineTransformRotate(transform, M_PI / 2.0);
0.             break;
0.         default:
0.             [NSException raise:NSInternalInconsistencyException format:@"Invalid?image?orientation"];
0.             break;
0.     }
0.     UIGraphicsBeginImageContext(bounds.size);
0.     CGContextRef context = UIGraphicsGetCurrentContext();
0.     if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft)
0.     {
0.         CGContextScaleCTM(context, -scaleRatio, scaleRatioheight);
0.         CGContextTranslateCTM(context, -height, 0);
0.     }
0.     else
0.     {
0.         CGContextScaleCTM(context, scaleRatio, -scaleRatioheight);
0.         CGContextTranslateCTM(context, 0, -height);
0.     }
0.     CGContextConcatCTM(context, transform);
0.     CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);
0.     UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
0.     UIGraphicsEndImageContext();
0.     return imageCopy;
0. }

來源:http://blog.sina.com.cn/s/blog_6568e7880100lvmu.html