缩放 UIImage/CGImage

发布于 2024-12-28 10:54:11 字数 1046 浏览 0 评论 0原文

我正在使用 AVFoundation 在相机应用程序中实现缩放功能。我像这样缩放预览视图：

[videoPreviewView setTransform:CGAffineTransformMakeScale(cameraZoom, cameraZoom)];

现在，在拍照后，我想在将图片保存到相机胶卷之前使用 cameraZoom 值缩放/裁剪图片。我应该如何最好地做到这一点？

编辑：使用贾斯汀的答案：

CGRect imageRect = CGRectMake(0.0f, 0.0f, image.size.width, image.size.height);

CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], imageRect);

CGContextRef bitmapContext = CGBitmapContextCreate(NULL, CGImageGetWidth(imageRef), CGImageGetHeight(imageRef), CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), CGImageGetColorSpace(imageRef), CGImageGetBitmapInfo(imageRef));

CGContextScaleCTM(bitmapContext, scale, scale);
CGContextDrawImage(bitmapContext, imageRect, imageRef);

CGImageRef zoomedCGImage = CGBitmapContextCreateImage(bitmapContext);

UIImage* zoomedImage = [[UIImage alloc] initWithCGImage:imageRef];

它正在缩放图像，但它没有占据图像的中心，而是似乎占据了右上角的区域。（我并不积极）。

另一个问题（我应该在OP中更清楚）是图像保持相同的分辨率，但我宁愿将其裁剪下来。

原文

I am implementing a zooming feature in a camera app using AVFoundation. I am scaling my preview view like this:

[videoPreviewView setTransform:CGAffineTransformMakeScale(cameraZoom, cameraZoom)];

Now, after I take a picture, I would like to zoom/crop the picture with the cameraZoom value before I save it to the camera roll. How best should I do this?

Edit: Using Justin's answer:

CGRect imageRect = CGRectMake(0.0f, 0.0f, image.size.width, image.size.height);

CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], imageRect);

CGContextRef bitmapContext = CGBitmapContextCreate(NULL, CGImageGetWidth(imageRef), CGImageGetHeight(imageRef), CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), CGImageGetColorSpace(imageRef), CGImageGetBitmapInfo(imageRef));

CGContextScaleCTM(bitmapContext, scale, scale);
CGContextDrawImage(bitmapContext, imageRect, imageRef);

CGImageRef zoomedCGImage = CGBitmapContextCreateImage(bitmapContext);

UIImage* zoomedImage = [[UIImage alloc] initWithCGImage:imageRef];

It is zooming the image, but it is not taking the center of it, but rather seems to be taking the top right area. (I'm not positive).

The other problem, (I should have been clearer in the OP), is that the image remains the same resolution, but I would rather just crop it down.

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笑咖 2025-01-04 10:54:11

+ (UIImage*)croppedImageWithImage:(UIImage *)image zoom:(CGFloat)zoom
{
    CGFloat zoomReciprocal = 1.0f / zoom;

    CGPoint offset = CGPointMake(image.size.width * ((1.0f - zoomReciprocal) / 2.0f), image.size.height * ((1.0f - zoomReciprocal) / 2.0f));
    CGRect croppedRect = CGRectMake(offset.x, offset.y, image.size.width * zoomReciprocal, image.size.height * zoomReciprocal);

    CGImageRef croppedImageRef = CGImageCreateWithImageInRect([image CGImage], croppedRect);

    UIImage* croppedImage = [[UIImage alloc] initWithCGImage:croppedImageRef scale:[image scale] orientation:[image imageOrientation]];

    CGImageRelease(croppedImageRef);

    return croppedImage;
}

+ (UIImage*)croppedImageWithImage:(UIImage *)image zoom:(CGFloat)zoom
{
    CGFloat zoomReciprocal = 1.0f / zoom;

    CGPoint offset = CGPointMake(image.size.width * ((1.0f - zoomReciprocal) / 2.0f), image.size.height * ((1.0f - zoomReciprocal) / 2.0f));
    CGRect croppedRect = CGRectMake(offset.x, offset.y, image.size.width * zoomReciprocal, image.size.height * zoomReciprocal);

    CGImageRef croppedImageRef = CGImageCreateWithImageInRect([image CGImage], croppedRect);

    UIImage* croppedImage = [[UIImage alloc] initWithCGImage:croppedImageRef scale:[image scale] orientation:[image imageOrientation]];

    CGImageRelease(croppedImageRef);

    return croppedImage;
}

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