正確調整iPhone圖片庫中的方形裁剪圖像大小的正確方法

Question

我想從照片庫上傳一些正方形裁剪的圖像，但是以某種方式上傳的圖像的長寬比將被破壞。 我不明白為什么，因為我將其裁剪為440 x 440，所以比例應該相同。

如果有人可以向我展示正確的方式如何將圖像裁剪為正方形並調整其大小而不會造成任何變形和質量損失，我將非常高興。 我只需要處理設備照片庫中的圖像即可。

- (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上創建類別

@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

Answer 2

drawInRect:強制圖像改變其縱橫比以適合正方形區域。 您需要使用原始縱橫比計算出一個覆蓋正方形區域的區域。

來自UIImage 類別的代碼可以執行以下操作：

- (UIImage *)imageCroppedToFill:(CGSize)size
{
    CGFloat factor = MAX(size.width / self.size.width,
                         size.height / self.size.height);

    UIGraphicsBeginImageContextWithOptions(size,
                                           YES,                     // Opaque
                                           self.scale);             // Use image scale

    CGRect rect = CGRectMake((size.width - nearbyintf(self.size.width * factor)) / 2.0,
                             (size.height - nearbyintf(self.size.height * factor)) / 2.0,
                             nearbyintf(self.size.width * factor),
                             nearbyintf(self.size.height * factor));
    [self drawInRect:rect];
    UIImage * croppedImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    NBULogInfo(@"Image %@ %@ cropped to %@ %@",
               self,
               NSStringFromCGSize(self.size),
               croppedImage,
               NSStringFromCGSize(croppedImage.size));

    return croppedImage;
}

Answer 3

您可以使用CoreGraphics動態繪制蒙版。 檢查一下，希望對您有所幫助；

https://stackoverflow.com/a/9585892/2622013