CODEWITHSUNDEEP
iosobjective-cuiimagecgfloat
Chisx
Chisx

Reputation: 1986

How to determine correct CGFloat values for desired UIImage Crop iOS 8.4

Currently I am cropping the UIImage received from my UIImagePickerController with this method:

- (UIImage *)imageByCroppingImage:(UIImage *)image toSize:(CGSize)size
{
    double refWidth = CGImageGetWidth(image.CGImage);
    double refHeight = CGImageGetHeight(image.CGImage);

    double x = (refWidth - size.width) / 2.0;
    double y = (refHeight - size.height) / 2.0;

    CGRect cropRect = CGRectMake(x, y, size.height, size.width);
    CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], cropRect);

    UIImage *cropped = [UIImage imageWithCGImage:imageRef scale:0.0 orientation:image.imageOrientation];
    CGImageRelease(imageRef);

    return cropped;
}

I am trying to accurately, with complete precision, grab the square photo in the middle of the UIImagePickerControllerOriginalImage. To do so, I am using the method above in my method that triggers when the user has clicked "Use Photo" from the UIImagePickerController:

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    picker.cameraFlashMode = UIImagePickerControllerCameraFlashModeOff;

    picker.allowsEditing = YES;
    UIImage *img = [info objectForKey:UIImagePickerControllerOriginalImage];
    UIImageWriteToSavedPhotosAlbum(img,nil,nil,nil);

    CGRect cropRect = CGRectMake(264, 0, 2448, 3000);
    CGSize sizeOfCrop = CGSizeMake(2550, 2500);  //<---NEED HELP, float sizes for photo of size 320x320(640x640)?

    UIImage *croppedImage = [self imageByCroppingImage:img toSize:sizeOfCrop]; //cropping the UIImage  

    UINavigationController *postControl = [self.storyboard instantiateViewControllerWithIdentifier:@"postControl"];
    RGPostViewController *postView = (RGPostViewController *)postControl.topViewController;

    [postView storeImage:imageToPass]; //store image in destinationViewController
    [self.presentedViewController presentViewController:postControl animated:NO completion:nil];
}

This code works correctly and does grab the center of the original image as I had hoped. The problem is that I do not know the correct CGFloat values to provide CGSize sizeOfCrop, the part where I added the comment "<--NEED HELP".

What CGFloat values must I pass to CGSizeMake in order to grab an exact perfect square picture from the middle? A picture that would perfectly fit an UIImageView with CGRect of width-height 320x320.

Upvotes: 0

Views: 269

Answers (1)

brandonscript
brandonscript

Reputation: 72965

You can apply my comment to both height and width. Since you're dealing with a constant center point, you just need the delta between widths and heights, then divide by 2 to get the origin point. And since you already know the originating size and the target (crop) size, you can just draw the original image into the crop rect:

CGFloat cropWidth = 320;
CGFloat cropHeight = 320;

CGSize cropSize = CGSizeMake(cropWidth, cropHeight);
UIGraphicsBeginImageContext(cropSize);

CGFloat cropX = (originalImage.size.width / 2) - (cropWidth / 2);
CGFloat cropY = (originalImage.size.height / 2) - (cropHeight / 2);
CGSize cropRect = CGSizeMake(cropX, cropY, cropWidth, cropHeight);

[originalImage drawInRect:cropRect];

UIImage* croppedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

Caveat: This is untested. If it doesn't center properly, you should be able to use the principles in this answer to center the image.

Upvotes: 0

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