如何将UiImage裁剪为特定大小？

Question

嗨，我正在使用UIimage，我需要将图像裁剪为特定的尺寸，假设我的特定尺寸的宽度等于设备的宽度，高度固定为200。我尝试了以下示例

-(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];
}

以下是我的实际图像

裁剪后我变得像下面

我所有的示例都在拉伸图像，但是我不希望拉伸就需要缩放图像。我想念的地方在哪里？请帮助我。

Answer 1

您使用的代码将调整图像的大小，我们将其用于图像压缩或图像调整大小。 如果要裁剪图像，有两种方法。 1）选择图像后，允许用户进行编辑。 您可以通过将allowEditing属性添加到选择器来实现此目的，例如，

pickerView.allowEditing = true

这将为您提供矩形以裁剪图像，您可以从选择器视图的didFinish方法中检索编辑的图像

2）以编程方式

• 要以编程方式裁剪图像，您需要传递帧进行裁剪。

这是我正在使用的功能

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

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

上面的代码将返回您的裁剪图像。

Answer 2

这些会将您的图像裁剪为所需的尺寸。

- (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;
}

///您想要裁剪的位置。

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);

谢谢。 享受编码:)