iphone UIImage用法介绍

iphone UIImage用法介绍

1.根据给定得图片，从其指定区域截取一张新得图片 
-(UIImage *)getImageFromImage{ 
    //大图bigImage 
    //定义myImageRect，截图的区域 
    CGRect myImageRect = CGRectMake(10.0, 10.0, 57.0, 57.0); 
    UIImage* bigImage= [UIImage imageNamed:@"k00030.jpg"]; 
    CGImageRef imageRef = bigImage.CGImage; 
    CGImageRef subImageRef = CGImageCreateWithImageInRect(imageRef, myImageRect); 
    CGSize size; 
    size.width = 57.0; 
    size.height = 57.0; 
    UIGraphicsBeginImageContext(size); 
    CGContextRef context = UIGraphicsGetCurrentContext(); 
    CGContextDrawImage(context, myImageRect, subImageRef); 
    UIImage* smallImage = [UIImage imageWithCGImage:subImageRef]; 
    UIGraphicsEndImageContext(); 
    return smallImage; 
} 

2.针对ＵIImage得一些常用缩放得方法： 
-(UIImage*)resizedImage1:(UIImage*)inImage  inRect:(CGRect)thumbRect { 
    // Creates a bitmap-based graphics context and makes it the current context. 
    UIGraphicsBeginImageContext(thumbRect.size); 
    [inImage drawInRect:thumbRect]; 
    return UIGraphicsGetImageFromCurrentImageContext(); 
} 
-(UIImage*)resizedImage2:(UIImage*)inImage  inRect:(CGRect)thumbRect { 
    CGImageRef          imageRef = [inImage CGImage]; 
    CGImageAlphaInfo    alphaInfo = CGImageGetAlphaInfo(imageRef); 
    /* There's a wierdness with kCGImageAlphaNone  and CGBitmapContextCreate 
    see Supported Pixel Formats in the Quartz 2D Programming Guide 
    Creating a Bitmap Graphics Context section 
    only RGB 8 bit images with alpha of kCGImageAlphaNoneSkipFirst,         kCGImageAlphaNoneSkipLast, kCGImageAlphaPremultipliedFirst,and kCGImageAlphaPremultipliedLast, with a few other oddball image kinds are supported 
The images on input here are likely to be png or jpeg files*/ 
    if (alphaInfo == kCGImageAlphaNone) 
        alphaInfo = kCGImageAlphaNoneSkipLast; 
        // Build a bitmap context that's the size of the thumbRect 
       CGFloat bytesPerRow; 
    if( thumbRect.size.width > thumbRect.size.height ) { 
       bytesPerRow = 4 * thumbRect.size.width; 
    } else { 
       bytesPerRow = 4 * thumbRect.size.height; 
    } 
    CGContextRef bitmap = CGBitmapContextCreate(NULL, 
                                                        thumbRect.size.width,       // width 
                                                        thumbRect.size.height,      // height 
                                                        8, //CGImageGetBitsPerComponent(imageRef),  // really needs to always be 8 
                                                        bytesPerRow, //4 * thumbRect.size.width,    // rowbytes 
                                                        CGImageGetColorSpace(imageRef), 
                                                        alphaInfo 
); 
    // Draw into the context, this scales the image 
    CGContextDrawImage(bitmap, thumbRect, imageRef); 
    // Get an image from the context and a UIImage 
    CGImageRef  ref = CGBitmapContextCreateImage(bitmap); 
    UIImage*    result = [UIImage imageWithCGImage:ref]; 
    CGContextRelease(bitmap);   // ok if NULL 
    CGImageRelease(ref); 
    return result; 
} 
- (UIImage *)scaleImage:(UIImage *) image maxWidth:(float) maxWidth maxHeight:(float) maxHeight 
{ 
    CGImageRef imgRef = image.CGImage; 
    CGFloat width = CGImageGetWidth(imgRef); 
    CGFloat height = CGImageGetHeight(imgRef); 
    if (width <= maxWidth && height <= maxHeight) 
    { 
        return image; 
    } 
    CGAffineTransform transform = CGAffineTransformIdentity; 
    CGRect bounds = CGRectMake(0, 0, width, height); 
    if (width > maxWidth || height > maxHeight) 
    { 
        CGFloat ratio = width/height; 
        if (ratio > 1) 
        { 
            bounds.size.width = maxWidth; 
            bounds.size.height = bounds.size.width / ratio; 
        } 
        else 
        { 
            bounds.size.height = maxHeight; 
             bounds.size.width = bounds.size.height * ratio; 
        } 
    } 
    CGFloat scaleRatio = bounds.size.width / width; 
    UIGraphicsBeginImageContext(bounds.size); 
    CGContextRef context = UIGraphicsGetCurrentContext(); 
    CGContextScaleCTM(context, scaleRatio, -scaleRatio); 
    CGContextTranslateCTM(context, 0, -height); 
    CGContextConcatCTM(context, transform); 
    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef); 
    UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 
    return imageCopy; 
} 

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