ios - 正确调整iPhone图片库中的方形裁剪图像大小的正确方法

Question

我想从照片库上传一些方形裁剪的图像，但是以某种方式上传的图像的长宽比将被破坏。我不明白为什么，因为我将其裁剪为440 x 440，所以比例应该相同。

如果有人可以向我展示正确的方式如何将图像裁剪为正方形并调整其大小而没有任何变形和质量损失，我将非常高兴。我只需要处理设备照片库中的图像即可。

- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex
{

    else if (buttonIndex == 1)
    {
        if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypePhotoLibrary] == YES) {

            UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
            imagePicker.sourceType =  UIImagePickerControllerSourceTypePhotoLibrary;

            imagePicker.delegate = self;

            imagePicker.allowsEditing = YES;
            [self presentViewController:imagePicker animated:YES completion:nil];
            [self.tableView reloadData];
        }
    }
}

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{

    UIImage *image = [info objectForKey:@"UIImagePickerControllerOriginalImage"];

    [picker dismissViewControllerAnimated:YES completion:nil];

    // resize image
    UIGraphicsBeginImageContext(CGSizeMake(440, 440));
    [image drawInRect: CGRectMake(0, 0, 440, 440)];
    UIImage *smallImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    NSData *imageData = UIImageJPEGRepresentation(smallImage, 1.0);
    [self uploadImage:imageData];
}

Answer 1

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{    
    UIImage *image = [info objectForKey:@"UIImagePickerControllerOriginalImage"];

    [picker dismissViewControllerAnimated:YES completion:nil];

    // Fixing orientation and transform of picked image
    image = [image fixOrientation];

    // Crop the image
    UIImage *smallImage = [image cropToRect:CGRectMake(0, 0, 440, 440)];

    NSData *imageData = UIImageJPEGRepresentation(smallImage, 1.0);
    [self uploadImage:imageData];
}

使用以下方法在UIImage上创建类别

@implementation UIImage (FixOrientation)

- (UIImage *)cropToRect:(CGRect)rect {
    rect.size.height = rect.size.height * [self scale];
    rect.size.width = rect.size.width * [self scale];
    rect.origin.x = rect.origin.x * [self scale];
    rect.origin.y = rect.origin.y * [self scale];
    CGImageRef sourceImageRef = [self CGImage];
    CGImageRef newImageRef = CGImageCreateWithImageInRect(sourceImageRef, rect);
    UIImage *newImage = [UIImage imageWithCGImage:newImageRef scale:[self scale] orientation:[self imageOrientation]];
    CGImageRelease(newImageRef);

    return newImage;
}

- (UIImage *)fixOrientation
{        
    // No-op if the orientation is already correct
    if (self.imageOrientation == UIImageOrientationUp) return self;

    // We need to calculate the proper transformation to make the image upright.
    // We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored.
    CGAffineTransform transform = CGAffineTransformIdentity;

    switch (self.imageOrientation) {
        case UIImageOrientationDown:
        case UIImageOrientationDownMirrored:
            transform = CGAffineTransformTranslate(transform, self.size.width, self.size.height);
            transform = CGAffineTransformRotate(transform, M_PI);
            break;

        case UIImageOrientationLeft:
        case UIImageOrientationLeftMirrored:
            transform = CGAffineTransformTranslate(transform, self.size.width, 0);
            transform = CGAffineTransformRotate(transform, M_PI_2);
            break;

        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            transform = CGAffineTransformTranslate(transform, 0, self.size.height);
            transform = CGAffineTransformRotate(transform, -M_PI_2);
            break;
        case UIImageOrientationUp:
        case UIImageOrientationUpMirrored:
            break;
    }

    switch (self.imageOrientation) {
        case UIImageOrientationUpMirrored:
        case UIImageOrientationDownMirrored:
            transform = CGAffineTransformTranslate(transform, self.size.width, 0);
            transform = CGAffineTransformScale(transform, -1, 1);
            break;

        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRightMirrored:
            transform = CGAffineTransformTranslate(transform, self.size.height, 0);
            transform = CGAffineTransformScale(transform, -1, 1);
            break;
        case UIImageOrientationUp:
        case UIImageOrientationDown:
        case UIImageOrientationLeft:
        case UIImageOrientationRight:
            break;
    }

    // Now we draw the underlying CGImage into a new context, applying the transform
    // calculated above.
    CGContextRef ctx = CGBitmapContextCreate(NULL, self.size.width, self.size.height,
                                             CGImageGetBitsPerComponent(self.CGImage), 0,
                                             CGImageGetColorSpace(self.CGImage),
                                             CGImageGetBitmapInfo(self.CGImage));
    CGContextConcatCTM(ctx, transform);
    switch (self.imageOrientation) {
        case UIImageOrientationLeft:
        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            // Grr...
            CGContextDrawImage(ctx, CGRectMake(0,0,self.size.height,self.size.width), self.CGImage);
            break;

        default:
            CGContextDrawImage(ctx, CGRectMake(0,0,self.size.width,self.size.height), self.CGImage);
            break;
    }

    // And now we just create a new UIImage from the drawing context
    CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
    UIImage *img = [UIImage imageWithCGImage:cgimg];
    CGContextRelease(ctx);
    CGImageRelease(cgimg);
    return img;
}

@end