I'm subclassing UIImageView to create a tile-based application. Essentially, I am taking a single image file and breaking it up into pieces, and then assigning the pieces to my tiles (UIImageViews), so that they can be manipulated independently.
What's the best way to grab a portion of an image and use that to draw a UIImageView? I thought about overriding drawRect and using CGAffineTransform, but it seems like there ought to be a simpler way to do this, perhaps by specifying a CGRect to the UIImage that is passed to the UIImageView, but I don't see an API for this.
Here we go:
UIImage* img = [UIImage imageNamed:#"myImage.jpg"];
CGRect imgFrame = CGRectMake(x, y, tileWidth, tileHeight);
CGImageRef imageRef = CGImageCreateWithImageInRect([img CGImage], imgFrame);
UIImage* subImage = [UIImage imageWithCGImage: imageRef];
CGImageRelease(imageRef);
Related
I am creating a "cartoonizer" application, which takes an image as an input and modifies it so as to format it in comics style.
At the moment, the original image is stored in a UIImageView, and I access to it by doing:
imageView.image
I was wondering whether it is possible to position an object on the image imageView.image (like a balloon) and then store the image with the object on it, like if it was originally part of the image content.
Thank you in advance.
You can do it like this, assuming you have correct opacity in the top image.
Like you said you get your image from imageView.image:
From here: blend two uiimages based on alpha/transparency of top image
UIImage *bottomImage = [UIImage imageNamed:#"bottom.png"];
UIImage *image = [UIImage imageNamed:#"top.png"];
CGSize newSize = CGSizeMake(width, height);
UIGraphicsBeginImageContext( newSize );
// Use existing opacity as is
[bottomImage drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
// Apply supplied opacity
[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height) blendMode:kCGBlendModeNormal alpha:0.8];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
More compositing techniques here: http://mobile.tutsplus.com/tutorials/iphone/ios-sdk-advanced-uiimage-techniques/
In my app, the user is able to put stickers on top of a photo. When they go to save their creation, I do a screen grab and store it in a UIImage:
UIGraphicsBeginImageContextWithOptions(self.mainView.bounds.size, NO, [UIScreen mainScreen].scale);
[self.mainView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *resultImage = [UIGraphicsGetImageFromCurrentImageContext() retain];
UIGraphicsEndImageContext();
(where self.mainView has a subview UIImageView which holds the photo, and another subview UIView which holds the stickers).
I am wondering, is it possible to do a screen shot in this manner, and maintain the resolution of the aforementioned photo?
The following will 'flatten' two UIImages into one while maintaining the resolution of the original image(s):
CGSize photoSize = photoImage.size;
UIGraphicsBeginImageContextWithOptions(photoSize, NO, 0.0);
CGRect photoRect = CGRectMake(0, 0, photoSize.width, photoSize.height);
// Add the original photo into the context
[photoImage drawInRect:photoRect];
// Add the sticker image with its upper left corner set to where the user placed it
[stickerImage drawAtPoint:stickerView.frame.origin];
// Get the resulting 'flattened' image
UIImage *flattenedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
The above assumes photoImage and stickerImage are both instances of UIImage and stickerView is a UIView with containing the stickerImage and thus will be able to use the stickerView frame to determine its origin.
If you have multiple stickers, just iterate through the collection.
If you are looking to save an image of your current view then this might help you.
UIGraphicsBeginImageContext(self.scrollView.contentSize);
[self.scrollView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *finalImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
CGImageRef imageRef = CGImageCreateWithImageInRect(finalImage.CGImage,
CGRectMake(scrollView.contentOffset.x, scrollView.contentOffset.y,
scrollView.frame.size.width, scrollView.frame.size.height));
UIImage *screenImage = [UIImage imageWithCGImage:imageRef scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp];
CGImageRelease(imageRef);
I'm attempting to create a UIImage and save it to the photo gallery, the image gets created but it's just a plane white with no color what so ever. Any ideas?
UIGraphicsBeginImageContext(CGSizeMake(320,420));
CGContextRef ctx = UIGraphicsGetCurrentContext();
UIImage *image = [[UIImage alloc] init];
[image drawInRect:CGRectMake(0, 0, 100, 100)];
UIImage *newImage;
newImage = UIGraphicsGetImageFromCurrentImageContext();
UIImageWriteToSavedPhotosAlbum(newImage, self, #selector(image:didFinishSavingWithError:ctx:), nil);
Also just to add to the above. I added this line:
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
And now I get a grey image, still no rectangle, but it's something different so thought it might help
What UIImage are you trying to show?, this code only initialized a space of memory but it's filled with nothing, use [UIImage imageNamed:#"..."]; where the string is some file the resources for your project. Then once you have opened and drawn the image in the context you will be able to draw a string or whatever over it.
Also make sure that you close the context once you have gotten the image from it.
I want to know, how can I erase a custom rect (with, for example, an UIView in IB or something else) of an UIImageView in order to display an other UIImageView positioned underneath.
I didn't manage to do it using some response in the forum...
This will clear a rect in an image:
- (UIImage *)clearRect:(CGRect)rect inImage:(UIImage *)image {
if (UIGraphicsBeginImageContextWithOptions != NULL)
UIGraphicsBeginImageContextWithOptions([image size], NO, 0.0);
else
UIGraphicsBeginImageContext([image size]);
CGContextRef context = UIGraphicsGetCurrentContext();
[image drawInRect:CGRectMake(0.0, 0.0, [image size].width, [image size].height)];
CGContextClearRect(context, rect);
UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return result;
}
Just load your image and clear the rects before assigning it to the image view:
UIImage *image = [UIImage imageNamed:#"Image.png"];
UIImage *maskedImage = [self clearRect:CGRectMake(10.0, 10.0, 50.0, 50.0) inImage:image];
[imageView setImage:maskedImage];
probably not the best solution but you can do the other way and take the 4 parts around the rect separately and combine them afterwards without the inner rect. You would repeat this as long as you have rect's to crop out.
You cannot clear the UIImageView itself because this just draws the UIImage. So you have erase the rect in the UIImage. Create a bitmap context, draw the image into it. Erase the part you want to "see through" with CGContextClearRect. When create a new new image from the bitmap context.
If I have a image size 1024*768, but I want to show a 100*100 square located on 200, 200. What is the simplest way to do it? Thz u.
You're basically talking about a "Crop" operation.
From HitScan in this question:
CGImageRef imageRef = CGImageCreateWithImageInRect([largeImage CGImage], cropRect);
// or use the UIImage wherever you like
[UIImageView setImage:[UIImage imageWithCGImage:imageRef]];
CGImageRelease(imageRef);