In the photo albums app there's a build in edit -> cropping tool. Is it possible to use that tool in an app instead of writing it on my own? Is it a part of the framework?
No, there is no built-in crop tool. However, it would not be that hard to write such a tool.
You'd need to create a control that let the user drag around an image in a scroll view, and collect the coordinates.
Then you'd create a graphics context and use the UIImage method drawInRect: to draw the image into a rect that's larger than the graphics context. The result would be to draw a cropped portion of the image into the context. Then you'd extract an image from the graphics context and discard the graphics context.
No that is not part of SDK, but you can easily crop images in iOS.
- (UIImage *)resizeImage:(UIImage *)image width:(float)w height:(float)h {
UIImage *croppedImage = image;
CGSize size = CGSizeMake(w, h);
UIGraphicsBeginImageContext(size);
CGRect rect = CGRectMake(0.0f, 0.0f, size.width, size.height);
[image drawInRect:rect];
croppedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return croppedImage;
}
I created a crop tool that might fit your need. It's not based on a scroll view, but rather letting the user choose a frame around their image.
https://github.com/nicholjs/BFCropInterface
Related
I'm trying to save the currently shown views on my iOS device for a certain app, and this is working properly. But I've got a problem as soon as I'm trying to save a UIImageView in Landscape orientation.
See the following image that describes my problem:
I'm using Auto layout for this app, and it runs on both iPhone and iPad. It seems like the ImageView is always saved as shown in portrait mode, and I'm a little bit stuck right now.
This is the code I use:
CGSize frameSize = self.view.frame.size;
if (UIInterfaceOrientationIsLandscape(self.interfaceOrientation)) {
frameSize = CGSizeMake(self.view.frame.size.height, self.view.frame.size.width);
}
UIGraphicsBeginImageContextWithOptions(frameSize, NO, 0.0);
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGFloat scale = CGRectGetWidth(self.view.frame) / CGRectGetWidth(self.view.bounds);
CGContextScaleCTM(ctx, scale, scale);
[self.view.layer renderInContext:ctx];
[self.delegate photoSaved:UIGraphicsGetImageFromCurrentImageContext()];
UIGraphicsEndImageContext();
Looking forward to your help!
I still have no idea what your exact issue is but using your screenshot code makes a bit strange image (not rotated or anything though, just too small). Can you try this code instead please.
+ (UIImage *)imageFromView:(UIView *)view {
UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, .0f);
[view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage * img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return img;
}
Other then that you must understand there is a huge difference between UIImage and CGImage as the UIImage includes the orientation while CGImage does not. When dealing with image transformations it is usually with the CGImage and getting its width or height will discard the orientation. That means a CGImage will have flipped dimensions when its orientation is not up (UIImageOrientationUp). But usually when dealing with such images you create a CGImage from the context and then use [UIImage imageWithCGImage:ref scale:1.0f orientation:originalOrientation]. Only if you wish to explicitly rotate the image so it has no orientation (being UIImageOrientationUp) you need to rotate and translate the image and draw it onto the context.
Anyway, this orientation issues are quite fixed by now, UIImagePNGRepresentation respects the orientation and you have an image constructor from the CGImage already written above which is what used to be missing in the past if I remember correctly.
After successfully using UIView’s new drawViewHierarchyInRect:afterScreenUpdates: method introduced in iOS 7 to obtain an image representation (via UIGraphicsGetImageFromCurrentImageContext()) for blurring my app also needed to obtain just a portion of a view. I managed to get it in the following manner:
UIImage *image;
CGSize blurredImageSize = [_blurImageView frame].size;
UIGraphicsBeginImageContextWithOptions(blurredImageSize, YES, .0f);
[aView drawViewHierarchyInRect: [aView bounds] afterScreenUpdates: YES];
image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
This lets me retrieve aView’s content following _blurImageView’s frame.
Now, however, I would need to obtain a portion of aView, but this time this portion would be “inside”. Below is an image representing what I would like to achieve.
I have already tried creating a new graphics context and setting its size to the portion’s size (red box) and calling aView to draw in the rect that represents the red box’s frame (of course its superview’s frame being equal to aView’s) but the image obtained is all black (empty).
After a lot of tweaking I managed to find something that did the job, however I heavily doubt this is the way to go.
Here’s my [edited-for-Stack Overflow] code that works:
- (UIImage *) imageOfPortionOfABiggerView
{
UIView *bigViewToExtractFrom;
UIImage *image;
UIImage *wholeImage;
CGImageRef _image;
CGRect imageToExtractFrame;
CGFloat screenScale = [[UIScreen mainScreen] scale];
// have to scale the rect due to (I suppose) the screen's scale for Core Graphics.
imageToExtractFrame = CGRectApplyAffineTransform(imageToExtractFrame, CGAffineTransformMakeScale(screenScale, screenScale));
UIGraphicsBeginImageContextWithOptions([bigViewToExtractFrom bounds].size, YES, screenScale);
[bigViewToExtractFrom drawViewHierarchyInRect: [bigViewToExtractFrom bounds] afterScreenUpdates: NO];
wholeImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// obtain a CGImage[Ref] from another CGImage, this lets me specify the rect to extract.
// However since the image is from a UIView which are all at 2x scale (retina) if you specify a rect in points CGImage will not take the screen's scale into consideration and will process the rect in pixels. You'll end up with an image from the wrong rect and half the size.
_image = CGImageCreateWithImageInRect([wholeImage CGImage], imageToExtractFrame);
wholeImage = nil;
// have to specify the image's scale due to CGImage not taking the screen's scale into consideration.
image = [UIImage imageWithCGImage: _image scale: screenScale orientation: UIImageOrientationUp];
CGImageRelease(_image);
return image;
}
I hope this will help anyone that stumped upon my issue. Feel free to improve my snippet.
Thanks
I would like to take an image and duplicate it. Then increase it by 105% and overlay it on the original image.
What is the correct way to do this on iOS?
This is your basic code for drawing the image and then saving it as an image again:
- (UIImage *)renderImage:(UIImage *)image atSize:(CGSize)size
{
UIGraphicsBeginImageContext(size);
[image drawInRect:CGRectMake(0.0, 0.0, size.width, size.height)];
// draw anything else into the context
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
Where it says "draw anything else into the context" you can draw the image at a reduced size by setting the appropriate rect to draw in. Then, call the renderImage method with whatever size you want the full image to be. You can use CGContextSetAlpha to set the transparency.
I want to crop an ellipse from an image in ios. Using core image framework, I know know to crop a reactangular region.
Using core graphics, I am able to clip the elliptical region. But, the size of the cropped image is same as the size of the original image as I am applying mask to area outside the ellipse.
So, the goal is to crop the elliptical region from an image and size of cropped image won't exceed the rectangular bounds of that image.
Any help would be greatly appreciated. Thanks in advance.
You have to create a context in the correct size, try the following code:
- (UIImage *)cropImage:(UIImage *)input inElipse:(CGRect)rect {
CGRect drawArea = CGRectMake(-rect.origin.x, -rect.origin.y, input.size.width, input.size.height);
UIGraphicsBeginImageContext(rect.size);
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextAddEllipseInRect(ctx, CGRectMake(0, 0, rect.size.width, rect.size.height));
CGContextClip(ctx);
[input drawInRect:drawArea];
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return img;
}
Maybe you have to adjust the drawArea to your needs as i did not test it.
I use this method to resize an image to the double of its original dimensions:
- (UIImage *)doubleSizeImage:(UIImage *)image {
CGSize newSize = CGSizeMake(image.size.width*2, image.size.height*2);
UIGraphicsBeginImageContext(newSize);
CGContextSetInterpolationQuality(UIGraphicsGetCurrentContext(), kCGInterpolationHigh);
[image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
The fact is that the interpolation is still poor: I can see well the pixelated effect which, for example, iOS Safari doesn't have when zooming pages. So I was wondering if there a better way to upscale an image, also using a third party library/category or something like that? Thanks!
Any time you interpolate, you're going to get some kind of artifacts.
Safari doesn't get artifacts on the page because the page is essentially a vector document, with outline fonts and resizable objects—but if you look at a raster image on the page, you'll see that if you blow it up big enough, the image will indeed show artifacts. Safari is not immune; nothing is.