I am trying to crop part of an image taken with the iPhone's camera via the cropping(to:) method on a CGImage but I am encountering a weird phenomenon where my UIImage's dimensions are doubled when converted with .cgImage which, obviously, prevents me from doing what I want.
The flow is:
Picture is taken with the camera and goes into a full-screen imageContainerView
A "screenshot" of this imageContainerView is made with a UIView extension, effectively resizing the image to the container's dimensions
imageContainerView's .image is set to now be the "screenshot"
let croppedImage = imageContainerView.renderToImage()
imageContainerView.image = croppedImage
print(imageContainerView.image!.size) //yields (320.0, 568.0)
print(imageContainerView.image!.cgImage!.width, imageContainerView.image!.cgImage!.height) //yields (640, 1136) ??
extension UIView {
func renderToImage(afterScreenUpdates: Bool = false) -> UIImage {
let rendererFormat = UIGraphicsImageRendererFormat.default()
rendererFormat.opaque = isOpaque
let renderer = UIGraphicsImageRenderer(size: bounds.size, format: rendererFormat)
let snapshotImage = renderer.image { _ in
drawHierarchy(in: bounds, afterScreenUpdates: afterScreenUpdates)
}
return snapshotImage
}
}
I have been wandering around here with no success so far and would gladly appreciate a pointer or a suggestion on how/why the image size is suddenly doubled.
Thanks in advance.
This is because print(imageContainerView.image!.size) prints the size of the image object in points and print(imageContainerView.image!.cgImage!.width, imageContainerView.image!.cgImage!.height) print the size of the actual image in pixels.
On iPhone you are using there are 2 pixels for evert point in both horizontal and vertical. The UIImage scale property will give you the factor which in your case will be 2.
See this link iPhone Resolutions
Related
I am trying to convert UIView containing 2 UIImageView to UIImage. Almost everything is working fine, but on final conversion some transparent diagonal lines are shown in final UIImage. I cant understand why is this happening. If someone can help. Thanks.
extension UIView {
/**
Convert UIView to UIImage
*/
func toImage() -> UIImage {
UIGraphicsBeginImageContextWithOptions(self.bounds.size, self.isOpaque, 0.0)
self.drawHierarchy(in: self.bounds, afterScreenUpdates: false)
let snapshotImageFromMyView = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return snapshotImageFromMyView!
}
}
following are before and after saving image
enter image descriptBefore SavingAfter Saving
I found the problem, my code was converting resulting UIImage to Webp at 0.70 quality. That was adding lines in image. By saving jpg and then converting to webp fixed the problem.
According to Apple docs, filters property of CALayer is not supported in iOS. As i used one of the apps which are applying CIFilter to UIView i.e. Splice, Video Editor Videoshow FX for Funimate and artisto. That's means we can apply CIFilter to UIView.
I have used SCRecorder library and try to get this task done by SCPlayer and SCFilterImageView. But i am facing black screen issue when video is playing after apply CIFilter. So kindly help me to complete this task so that i can apply CIFilter to UIView and also can change the filter by clicking on a UIButton.
The technically accurate answer is that a CIFilter requires a CIImage. You can turn a UIView into a UIImage and then convert that into a CIImage, but all CoreImage filters that use an image for input (there are some that generate a new image) use a `CIImage for input and output.
Please note that the origin for a CIImage is bottom left, not top left. Basically the Y axis is flipped.
If you use CoreImage filters dynamically, learn to use a GLKView to render in - it uses the GPU where a UIImageView uses the CPU.
If you want to test out a filter, it's best to use an actual device. The simulator will give you very poor performance. I've seen a simple blur take nearly a minute where on a device it will be a fraction of a second!
Let's say you have a UIView that you wish to apply a CIPhotoEffectMono to. The steps to do this would be:
Convert the UIView into a CIImage.
Apply the filter, getting a CIImage as output.
Use a CIContext to create a CGImage and then convert that to a UIImage.
Here's a UIView extension that will convert the view and all it's subviews into a UIImage:
extension UIView {
public func createImage() -> UIImage {
UIGraphicsBeginImageContextWithOptions(
CGSize(width: self.frame.width, height: self.frame.height), true, 1)
self.layer.render(in: UIGraphicsGetCurrentContext()!)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return image!
}
}
Converting a UIImage into a CIImage is one line of code:
let ciInput = CIImage(image: myView.createImage)
Here's a function that will apply the filter and return a UIImage:
func convertImageToBW(image:UIImage) -> UIImage {
let filter = CIFilter(name: "CIPhotoEffectMono")
// convert UIImage to CIImage and set as input
let ciInput = CIImage(image: image)
filter?.setValue(ciInput, forKey: "inputImage")
// get output CIImage, render as CGImage first to retain proper UIImage scale
let ciOutput = filter?.outputImage
let ciContext = CIContext()
let cgImage = ciContext.createCGImage(ciOutput!, from: (ciOutput?.extent)!)
return UIImage(cgImage: cgImage!)
}
I usually scale the image of an imageView in Android with the scaleX and scaleY properties.
How can I do the same in IOS? I'm really new with IOS,I'm using swift 3 and I didn't find any analog thing like that.
If you need to scale the image proportionally, the following code might work for you:
if let cgImage = imageView.image?.cgImage, let orientation = imageView.image?.imageOrientation {
imageView.image = UIImage(cgImage: cgImage, scale: newScale, orientation: orientation)
}
However, if you only want to display it with a size different than that of the original image, you should control the size of the image using the size of the UIImageView that presents it. To make sure the image scales correctly with the size of the view, take a look at the UIImageView.contentMode property: https://developer.apple.com/reference/uikit/uiview/1622619-contentmode
I am using AVCapture+camera portrait mode to capture an image. when I display the captured image, it is fine--looks fine. But when I convert to jpeg representation and then convert to base64 string to server and server stored it, it is "rotated" already.
So I checked the image orientation before sending to server: it is UIImageOrientation.Right(so is there any way to capture an image using portrait mode but the captured image orientation is up? well, I doubt that after some digging). After the server got the image, it did not do anything, just ignored the metadata about orientation I guess.
since the image I captured looks fine, I want just preserve how the image look like. However, I want to set the image orientation to be up. if I just set the image orientation, the image does not look right anymore.
So is there a way to set the orientation without causing the image to be rotated or after setting the orientation to be up, how to I keep the orientation but rotate the actual image to make it look right?
- (UIImage *)removeRotationForImage:(UIImage*)image {
if (image.imageOrientation == UIImageOrientationUp) return image;
UIGraphicsBeginImageContextWithOptions(image.size, NO, image.scale);
[image drawInRect:(CGRect){0, 0, image.size}];
UIImage *normalizedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return normalizedImage;
}
swift version of oldrinmendez answer
func removeRotationForImage(image: UIImage) -> UIImage {
if image.imageOrientation == UIImageOrientation.Up {
return image
}
UIGraphicsBeginImageContextWithOptions(image.size, false, image.scale)
image.drawInRect(CGRect(origin: CGPoint(x: 0, y: 0), size: image.size))
let normalizedImage: UIImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return normalizedImage
}
I am making drawing application where i need to draw image.
But when i try to to that image size is change. i want the same size of image after draw.
Here is my code
NSLog(#"%#",NSStringFromCGSize(self.image.size));
self.image = UIGraphicsGetImageFromCurrentImageContext();
NSLog(#"%#",NSStringFromCGSize(self.image.size));
O/p
2014-08-24 15:11:14.511 Demo[4877:60b] {877, 1136}
2014-08-24 15:11:15.533 Demo[4877:60b] {320, 460}
How can take image quality same as before Here image is scale down
//UIGraphicsBeginImageContext(imageView.frame.size)
//Use this:
let hasAlpha = true
let scale: CGFloat = 0.0 // Automatically use scale factor of main screen
let size = (size of your canvas / imageview)
UIGraphicsBeginImageContextWithOptions(size, !hasAlpha, scale) //use this
//Instead of this:
UIGraphicsBeginImageContext(imageView.frame.size) //dont use this