如何从 UIImagePickerController 设置保存图像的分辨率

How to set the resolution of a saved image from the UIImagePickerController(如何从 UIImagePickerController 设置保存图像的分辨率)

问题描述

我正在使用 UIImagePickerController 将图片从我的相机胶卷设置为 UIImageView.然而，图像在这个 UIImageView 内自动缩放，因为我在 IB 中提到了缩放以适应".我想以 80x80 像素的分辨率保存我选择的图像，这样我就不必缩放了.(由于这个扩展问题，我的应用程序变得非常缓慢.)

I'm using an UIImagePickerController to set a picture from my cameraroll to a UIImageView. However the image is getting scaled automaticly inside this UIImageView because I mentioned 'scale to fit' inside the IB. I'd like to save my chosen image with a resolution of 80x80 pixels so that I won't have to scale. (My App is getting realy slow because of this scaling issue.)

这是我的代码片段:

-(void)imagePickerController:(UIImagePickerController *)picker
      didFinishPickingImage : (UIImage *)image
                 editingInfo:(NSDictionary *)editingInfo
{
    [picker dismissModalViewControllerAnimated:YES];
    UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
        photoView.image = image;


        NSString *docDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];       
        NSString *pngFilePath = [NSString stringWithFormat:@"%@/foto1.png",docDir];
        NSData *data = [NSData dataWithData:UIImagePNGRepresentation(image)];

        [data writeToFile:pngFilePath atomically:YES];
}

非常感谢您的帮助！

推荐答案

我在这里找到了这段代码:链接

I found this code here: Link

//  ==============================================================
//  resizedImage
//  ==============================================================
// Return a scaled down copy of the image.  

UIImage* resizedImage(UIImage *inImage, 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
    CGContextRef bitmap = CGBitmapContextCreate(
                NULL,
                thumbRect.size.width,       // width
                thumbRect.size.height,      // height
                CGImageGetBitsPerComponent(imageRef),   // really needs to always be 8
                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;
}

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