如何将UiImage裁剪为特定大小？

Question

Hi I am working with the UIimage, I need to crop my image to specific size, Suppose my specific size width is equal to device width and height is fixed 200. I tried in Google lot of examples but non of those not working for me, I tried below samples

-(UIImage *)resizeImage:(UIImage *)image
{
    float h=200;
    float w=400;


    float actualHeight = image.size.height;
    float actualWidth = image.size.width;
    float maxHeight = h;
    float maxWidth = w;
    float imgRatio = actualWidth/actualHeight;
    float maxRatio = maxWidth/maxHeight;
    float compressionQuality = 0.8;//50 percent compression

    if (actualHeight > maxHeight || actualWidth > maxWidth)
    {
        if(imgRatio < maxRatio)
        {
            //adjust width according to maxHeight
            imgRatio = maxHeight / actualHeight;
            actualWidth = imgRatio * actualWidth;
            actualHeight = maxHeight;
        }
        else if(imgRatio > maxRatio)
        {
            //adjust height according to maxWidth
            imgRatio = maxWidth / actualWidth;
            actualHeight = imgRatio * actualHeight;
            actualWidth = maxWidth;
        }
        else
        {
            actualHeight = maxHeight;
            actualWidth = maxWidth;
        }
    }
    CGRect rect = CGRectMake(0.0, 0.0, actualWidth, actualHeight);
    UIGraphicsBeginImageContext(rect.size);
    //UIGraphicsBeginImageContextWithOptions(rect.size,NO,0.0);
    [image drawInRect:rect];
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    NSData *imageData = UIImageJPEGRepresentation(img, compressionQuality);
    UIGraphicsEndImageContext();
    return [UIImage imageWithData:imageData];
}

Below is my actual image

After cropping I am getting like below

All of my examples are stretching the image But i want with out stretching need to scale the image.Where i am missing?Please help me.

Answer 1

The code you are using will resize your image, We use it for image compression or image resizing. If you want to crop an Image there are two way. 1)Allow user to edit when image is selected. You can achieve this by adding allowEditing property to picker like,

pickerView.allowEditing = true

This will give you rectangle to crop image, you can retrieve edited image from didFinish method of picker view

2)Programatically

• To crop image programatically you need to pass frame for cropping.

Here is the function i am using

func croppImage(originalImage:UIImage, toRect rect:CGRect) -> UIImage{

var imageRef:CGImageRef = CGImageCreateWithImageInRect(originalImage.CGImage, rect)
var croppedimage:UIImage = UIImage(CGImage:imageRef)
return croppedimage
}

The above code will return you cropped image.

Answer 2

These will crop your image into size you required.

- (CGImageRef)newTransformedImage:(CGAffineTransform)transform
                      sourceImage:(CGImageRef)sourceImage
                       sourceSize:(CGSize)sourceSize
                sourceOrientation:(UIImageOrientation)sourceOrientation
                      outputWidth:(CGFloat)outputWidth
                         cropSize:(CGSize)cropSize
                    imageViewSize:(CGSize)imageViewSize
{
    CGImageRef source = [self newScaledImage:sourceImage
                             withOrientation:sourceOrientation
                                      toSize:sourceSize
                                 withQuality:kCGInterpolationNone];

    CGFloat aspect = cropSize.height/cropSize.width;
    CGSize outputSize = CGSizeMake(outputWidth, outputWidth*aspect);

    CGContextRef context = CGBitmapContextCreate(NULL,
                                                 outputSize.width,
                                                 outputSize.height,
                                                 CGImageGetBitsPerComponent(source),
                                                 0,
                                                 CGImageGetColorSpace(source),
                                                 CGImageGetBitmapInfo(source));
    CGContextSetFillColorWithColor(context, [[UIColor clearColor] CGColor]);
    CGContextFillRect(context, CGRectMake(0, 0, outputSize.width, outputSize.height));

    CGAffineTransform uiCoords = CGAffineTransformMakeScale(outputSize.width / cropSize.width,
                                                            outputSize.height / cropSize.height);
    uiCoords = CGAffineTransformTranslate(uiCoords, cropSize.width/2.0, cropSize.height / 2.0);
    uiCoords = CGAffineTransformScale(uiCoords, 1.0, -1.0);
    CGContextConcatCTM(context, uiCoords);

    CGContextConcatCTM(context, transform);
    CGContextScaleCTM(context, 1.0, -1.0);

    CGContextDrawImage(context, CGRectMake(-imageViewSize.width/2.0,
                                           -imageViewSize.height/2.0,
                                           imageViewSize.width,
                                           imageViewSize.height)
                       , source);

    CGImageRef resultRef = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    CGImageRelease(source);
    return resultRef;
}

- (CGImageRef)newScaledImage:(CGImageRef)source withOrientation:(UIImageOrientation)orientation toSize:(CGSize)size withQuality:(CGInterpolationQuality)quality
{
    CGSize srcSize = size;
    CGFloat rotation = 0.0;

    switch(orientation)
    {
        case UIImageOrientationUp: {
            rotation = 0;
        } break;
        case UIImageOrientationDown: {
            rotation = M_PI;
        } break;
        case UIImageOrientationLeft:{
            rotation = M_PI_2;
            srcSize = CGSizeMake(size.height, size.width);
        } break;
        case UIImageOrientationRight: {
            rotation = -M_PI_2;
            srcSize = CGSizeMake(size.height, size.width);
        } break;
        default:
            break;
    }

    CGContextRef context = CGBitmapContextCreate(NULL,
                                                 size.width,
                                                 size.height,
                                                 8,  //CGImageGetBitsPerComponent(source),
                                                 0,
                                                 CGImageGetColorSpace(source),
                                                 (CGBitmapInfo)kCGImageAlphaNoneSkipFirst  //CGImageGetBitmapInfo(source)
                                                 );

    CGContextSetInterpolationQuality(context, quality);
    CGContextTranslateCTM(context,  size.width/2,  size.height/2);
    CGContextRotateCTM(context,rotation);

    CGContextDrawImage(context, CGRectMake(-srcSize.width/2 ,
                                           -srcSize.height/2,
                                           srcSize.width,
                                           srcSize.height),
                       source);

    CGImageRef resultRef = CGBitmapContextCreateImage(context);
    CGContextRelease(context);

    return resultRef;
}

///where you want to crop.

CGImageRef imageRef = [self newTransformedImage:transform
                                    sourceImage:self.image.CGImage
                                     sourceSize:self.image.size
                              sourceOrientation:self.image.imageOrientation
                                    outputWidth:self.image.size.width
                                       cropSize:self.photoView.cropView.frame.size
                                  imageViewSize:self.photoView.photoContentView.bounds.size];

UIImage *image = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);

Thank you. Enjoy Coding :)