I create a picture programmatically, convert it to data and back and get different pictures.
let image1: UIImage = {
let size = CGSize(width: 50, height: 50)
let rect = CGRect(x: 0, y: 0, width: size.width, height: size.height)
UIGraphicsBeginImageContextWithOptions(size, false, 0)
UIColor.black.setFill()
UIRectFill(rect)
let image: UIImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
return image
}()
let data = UIImagePNGRepresentation(image1)!
let image2 = UIImage(data: data)!
print(image1.size) // (50.0, 50.0)
print(image2.size) // (100.0, 100.0)
Please explain what happens and how to solve the problem. Thank you!
The "culprit" line:
UIGraphicsBeginImageContextWithOptions(size, false, 0)
Looking at the doc of UIGraphicsBeginImageContextWithOptions(), for the last parameter (scale)
scale The scale factor to apply to the bitmap. If you specify a value of 0.0, the scale factor is set to the scale factor of the
device’s main screen.
If your device is Retina (*2), then the scale factor will be 2.
Related
I have the following functions.
extension UIImage
{
var width: CGFloat
{
return size.width
}
var height: CGFloat
{
return size.height
}
private static func circularImage(diameter: CGFloat, color: UIColor) -> UIImage
{
UIGraphicsBeginImageContextWithOptions(CGSize(width: diameter, height: diameter), false, 0)
let context = UIGraphicsGetCurrentContext()!
context.saveGState()
let rect = CGRect(x: 0, y: 0, width: diameter, height: diameter)
context.setFillColor(color.cgColor)
context.fillEllipse(in: rect)
context.restoreGState()
let image = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
return image
}
private func addCentered(image: UIImage, tintColor: UIColor) -> UIImage
{
let topImage = image.withTintColor(tintColor, renderingMode: .alwaysTemplate)
let bottomImage = self
UIGraphicsBeginImageContext(size)
let bottomRect = CGRect(x: 0, y: 0, width: bottomImage.width, height: bottomImage.height)
bottomImage.draw(in: bottomRect)
let topRect = CGRect(x: (bottomImage.width - topImage.width) / 2.0,
y: (bottomImage.height - topImage.height) / 2.0,
width: topImage.width,
height: topImage.height)
topImage.draw(in: topRect, blendMode: .normal, alpha: 1.0)
let mergedImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
return mergedImage
}
}
They work fine, but how do I properly apply UIScreen.main.scale to support retina screens?
I've looked at what's been done here but can't figure it out yet.
Any ideas?
Accessing UIScreen.main.scale itself is a bit problematic, as you have to access it only from main thread (while you usually want to put a heavier image processing on a background thread). So I suggest one of these ways instead.
First of all, you can replace UIGraphicsBeginImageContext(size) with
UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
The last argument (0.0) is a scale, and based on docs "if you specify a value of 0.0, the scale factor is set to the scale factor of the device’s main screen."
If instead you want to retain original image's scale on resulting UIImage, you can do this: after topImage.draw, instead of getting the UIImage with UIGraphicsGetImageFromCurrentImageContext, get CGImage with
let cgImage = context.makeImage()
and then construct UIImage with the scale and orientation of the original image (as opposed to defaults)
let mergedImage = UIImage(
cgImage: cgImage,
scale: image.scale,
orientation: image.opientation)
I have an image which is a bubble shape, and I wish to add text to the middle of the image, so I tried to use UIGraphicsBeginImageContextWithOptions to redraw the image.
The code is as following:
let imageSize = CGSize(width: 40, height: 40)
// the rect in which the image will be drawn in
let imageRect = CGRect(origin: CGPoint.zero, size: imageSize)
UIGraphicsBeginImageContextWithOptions(imageSize, true, 1.0)
// begining drawing things
// first, we draw the image in the specified rect
image.draw(in: imageRect)
let attributes = [ NSAttributedStringKey.foregroundColor: UIColor.red,
NSAttributedStringKey.font: UIFont.boldSystemFont(ofSize: 20)]
let text = "55"
let size = text.size(withAttributes: attributes)
let rect = CGRect(x: 20 - size.width / 2, y: 20 - size.height / 2, width: size.width, height: size.height)
text.draw(in: rect, withAttributes: attributes)
let newImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
return newImage
but I get a square with a black background with the desired image inside:
the blue is the original image, the black is the re-drawn image. Anyone knows how can I draw the image as the original image?
Thanks!
You need to pass false, not true, to the 2nd argument (the opaque parameter) of the call to UIGraphicsBeginImageContextWithOptions function.
UIGraphicsBeginImageContextWithOptions(imageSize, false, 1.0)
You should also pass 0 as the 3rd argument (scale) so the image is scaled to match the current device's screen scale.
I have multiple sizes of frames, which can be hard coded, or server will decide. I have to select Image from Gallery, which definitely can be of many dimensions.
I am selecting Image from Gallery
I am generating white background UIImage, using code.
let size = CGSize(width: 424/2, height: 664/2)
UIGraphicsBeginImageContextWithOptions(size, true, 0)
UIColor.white.setFill()
UIRectFill(CGRect(x: 0, y: 0, width: size.width, height: size.height))
let background_image: UIImage? = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
Now, what I want, to make another Image, which keep Leading 20 pixel, Top 20 Pixel, and width and height 20 pixel smaller than original background.
How can I achieve it.
What I tried before coming to StackOverflow.
func mergedImageWith(frontImage:UIImage?, backgroundImage: UIImage?) -> UIImage{
if (backgroundImage == nil) {
return frontImage!
}
let size = CGSize(width: 424/2, height: 664/2)
UIGraphicsBeginImageContextWithOptions(size, true, 0)
UIColor.white.setFill()
UIRectFill(CGRect(x: 0, y: 0, width: size.width, height: size.height))
let backgroundImage2: UIImage? = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
backgroundImage2?.draw(in: CGRect.init(x: 0, y: 0, width: size.width, height: size.height))
frontImage?.draw(in: getAspectFillFrame(sizeImageView: size2, sizeImage: (frontImage?.size)!))
let newImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
return newImage
}
here background image is created with aspect fill, but issue is of starting position and complete height and width.
In very simple words. Its like making custom frames and merge them with images(aspect fill) for printing.
can anyone help me out
Thanks.
Try not ending your image context until all of the images are drawn (I am also including some code that I have working, edited down a bit)
class layeredImageView: UIImageView {
var imageBackground:UIImage!
var imageForeground:UIImage!
UIGraphicsBeginImageContextWithOptions(self.frame.size, false, UIScreen.main.scale)
self.image?.draw(in: self.frame)
imageBackground.draw(in: CGRect(<rect>)
imageForeground.draw(in: CGRect(<rect>)
self.image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
}
Why does Xcode shows a image bigger then AS-IS?
http://users.telenet.be/thomazz/ScreenShot4.png
http://users.telenet.be/thomazz/ScreenShot3.png
Scenario:
I got an image.
I resize this UIImage.
I export the resized UIImage.
I comment out my resize code.
I import the resized image in Xcode.
problem 1: Xcode shows the image twice as big as normal.
problem 2: when I run my app with the exported-resized image, it is twice as big.
view screenshots.
This totally depends on your frame of your UIImageView and not its dimensions.
So if you have an 1024x1024 image and you place it in a 10x10 frame, it will render to 10x10 size and vice versa.
If you want it bigger, then make your UIImageView bigger
Edit: so it is a google maps icon
Set the resized image as marker icon ,i.e,
marker.icon = self.imageWithImage(image: UIImage(named: "imageName")!, scaledToSize: CGSize(width: 3.0, height: 3.0))
Add this function
func imageWithImage(image:UIImage, scaledToSize newSize:CGSize) -> UIImage{
UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0);
image.drawInRect(CGRectMake(0, 0, newSize.width, newSize.height))
let newImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage
}
Dear Mohammad Bashir Sidani, I have this code.
And this code works. but it creates a new UIImage.
Then I use UIImagePNGRepresentation(resizedImage) to export the image.
I disable the code below to use the "programmatically-resized image".
this new resized image is blown up by Xcode... :(
extension UIImage {
func resizeImage(_ dimension: CGFloat, opaque: Bool, contentMode: UIViewContentMode = .scaleAspectFit) -> UIImage {
var width: CGFloat
var height: CGFloat
var newImage: UIImage
let size = self.size
let aspectRatio = size.width/size.height
switch contentMode {
case .scaleAspectFit:
if aspectRatio > 1 { // Landscape image
width = dimension
height = dimension / aspectRatio
} else { // Portrait image
height = dimension
width = dimension * aspectRatio
}
default:
fatalError("UIIMage.resizeToFit(): FATAL: Unimplemented ContentMode")
}
if #available(iOS 10.0, *) {
let renderFormat = UIGraphicsImageRendererFormat.default()
renderFormat.opaque = opaque
let renderer = UIGraphicsImageRenderer(size: CGSize(width: width, height: height), format: renderFormat)
newImage = renderer.image {
(context) in
self.draw(in: CGRect(x: 0, y: 0, width: width, height: height))
}
} else {
UIGraphicsBeginImageContextWithOptions(CGSize(width: width, height: height), opaque, 0)
self.draw(in: CGRect(x: 0, y: 0, width: width, height: height))
newImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
}
return newImage
}
}
I am building a circle crop function in Swift. I pretty much have everything working however when I save the cropped photo it is slightly blurry:
Not sure if it is visible here or not but on my iPhone I can see a difference, slight blurring. I'm not zooming in more than the actual size of the image. I am using a UIScrollView with max zoom factor set to 1.0. The crop code is:
func didTapOk() {
let scale = scrollView.zoomScale
let newSize = CGSize(width: image!.size.width*scale, height: image!.size.height*scale)
let offset = scrollView.contentOffset
UIGraphicsBeginImageContext(CGSize(width: 240, height: 240))
let circlePath = UIBezierPath(ovalInRect: CGRect(x: 0, y: 0, width: 240, height: 240))
circlePath.addClip()
var sharpRect = CGRect(x: -offset.x, y: -offset.y, width: newSize.width, height: newSize.height)
sharpRect = CGRectIntegral(sharpRect)
image?.drawInRect(sharpRect)
let finalImage = UIGraphicsGetImageFromCurrentImageContext()
UIImageWriteToSavedPhotosAlbum(finalImage, nil, nil, nil)
}
Here I am trying to use CGRectIntegral to improve the result but it doesn't seem to make any difference. Any pointers on what I could do to improve this?
What's happening is your crop is blurring because it hasn't accounted for the scale of your screen (whether you're using a retina display etc).
Use UIGraphicsBeginImageContextWithOptions(CGSize(width: 240, height: 240), true, 0) to account for the retina screen. Check here for more details on how to use this function.
I suspect that, although the accepted answer above is working for you, it is only working due to the screen scale being the same as the image scale.
As you are not rendering your image from the screen itself (you're rendering from a UIImage to another UIImage), the screen scale should be irrelevant.
You should instead be passing in the scale of the image when you create your context, like so:
UIGraphicsBeginImageContextWithOptions(CGSize(width: 240, height: 240), false, image.scale)
Here's a way in Swift 3 to disable any interpolation.
UIGraphicsBeginImageContextWithOptions(imageSize, false, UIScreen.main.scale)
let context = UIGraphicsGetCurrentContext()
context?.interpolationQuality = CGInterpolationQuality.none
Additionally, since this is often for pixel drawing purposes, you may want to add:
// Ensure the image is not drawn upside down
context?.saveGState()
context?.translateBy(x: 0.0, y: maxHeight)
context?.scaleBy(x: 1.0, y: -1.0)
// Make the drawing
context?.draw(yourImage, in: CGRect(x: 0, y: 0, width: maxWidth, height: maxHeight))
// Restore the GState of the context
context?.restoreGState()