iPhone开发应用UIImage图片对象操作

iPhone开发应用UIImage图片对象操作是本文要介绍的内容，主要来学习UIImage图片对象操作，内容不多，主要是以代码实现图片对象的操作。

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;   
            boundsbounds.size.height = bounds.size.width / ratio;   
        }   
        else   
        {   
            bounds.size.height = maxHeight;   
             boundsbounds.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;   
            boundsbounds.size.height = bounds.size.width / ratio;   
        }   
        else   
        {   
            bounds.size.height = kMaxResolution;   
            boundsbounds.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;   
            boundsbounds.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;   
            boundsbounds.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;   
            boundsbounds.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;   
            boundsbounds.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;   
} 

小结：iPhone开发应用UIImage图片对象操作的内容介绍完了，希望通过本文的学习能对你有所帮助！