I have a UIImage extension that can change the color of it's image that I pulled off somewhere. The problem is that it downgrades it's resolution after it colors the image. I've seen other answers based on this, but I'm not sure how to adapt this to rendering a retina image in this instance:
extension UIImage {
func maskWithColor(color: UIColor) -> UIImage? {
let maskImage = cgImage!
let width = size.width
let height = size.height
let bounds = CGRect(x: 0, y: 0, width: width, height: height)
let colorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)
let context = CGContext(data: nil, width: Int(width), height: Int(height), bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)!
context.clip(to: bounds, mask: maskImage)
context.setFillColor(color.cgColor)
context.fill(bounds)
if let cgImage = context.makeImage() {
let coloredImage = UIImage(cgImage: cgImage)
return coloredImage
} else {
return nil
}
}
}
I've seen people using UIGraphicsBeginImageContextWithOptions and setting it's scale to the main screen, but I don't think it works if I'm using the CGContext function.
I think you want:
let width = size.width * scale
let height = size.height * scale
and:
let coloredImage = UIImage(cgImage: cgImage, scale:scale, orientation:.up)
(You may need to use imageOrientation instead of .up.)
Related
I have a round avatar image with a transparent background. I want to create a new round image of the same size out of the initial image, with a gradient background behind it. So it looks like standing in sky instead of having a transparent background.
Since I will use this image as tabbaritem’s image, I couldn’t use uiview and edit it’s background layer.
And to make it reusable I wanted to create a UIImage extension.
Below is what I do:
extension UIImage {
func gradientImage() -> UIImage? {
let width = self.size.width
let height = self.size.height
UIGraphicsBeginImageContextWithOptions(size, false, 0)
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)
let colorSpace = CGColorSpaceCreateDeviceRGB()
guard let bitmapContext = CGContext(data: nil,
width: Int(width),
height: Int(height),
bitsPerComponent: 8,
bytesPerRow: 0,
space: colorSpace,
bitmapInfo: bitmapInfo.rawValue) else { return nil }
let locations: [CGFloat] = [0.0, 1.0]
let top = R.color.duckDimDarkGrey()?.cgColor
let bottom = R.color.duckPencilDark()?.cgColor
let colors = [top, bottom] as CFArray
guard let gradient = CGGradient(colorsSpace: colorSpace, colors: colors, locations: locations) else {
return nil
}
bitmapContext.drawLinearGradient(gradient, start: CGPoint.zero, end: CGPoint(x: 0, y: size.height), options: CGGradientDrawingOptions())
guard let cgImage = UIGraphicsGetImageFromCurrentImageContext()?.cgImage else { return nil }
UIGraphicsEndImageContext()
let img = UIImage(cgImage: cgImage)
return img
}
}
Here is how I use it:
Let image1 = UIImage(named: “test.png”)
self.tabBar.items[3].image = image1.gradientImage()
However I am getting an empty image somehow.
I'm trying to extract the array of numbers from a UIImage in swift but at the end I got only a bunch of zeros no useful information at all.
that's the code I wrote to try accomplishing this.
var photo = UIImage(named: "myphoto.jpg")!
var withAlpha = true
var bytesPerPixels: Int = withAlpha ? 4 : 3
var width: Int = Int(photo.size.width)
var height: Int = Int(photo.size.height)
var bitsPerComponent: Int = 8
var bytesPerRow = bytesPerPixels * width
var totalPixels = (bytesPerPixels * width) * height
var alignment = MemoryLayout<UInt32>.alignment
var data = UnsafeMutableRawPointer.allocate(byteCount: totalPixels, alignment: alignment )
var bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedFirst.rawValue | CGBitmapInfo.byteOrder32Little.rawValue).rawValue
var colorSpace = CGColorSpaceCreateDeviceRGB()
let ctx = CGContext(data: data, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo)
let bindedPointer: UnsafeMutablePointer<UInt32> = data.bindMemory(to: UInt32.self, capacity: totalPixels)
var pixels = UnsafeMutableBufferPointer.init(start: bindedPointer, count: totalPixels)
for p in pixels{
print(p, Date())
}
At the end I tried to bind the unsafeMutableRawPointer to extract the values but got no success,
what could I be missing here?
Thank you all in advance.
A few observations:
You need to draw the image to the context.
I’d also suggest that rather than creating a buffer that you have to manage manually, that you pass nil and let the OS create (and manage) that buffer for you.
Note that totalPixels should be just width * height.
Your code assumes the scale of the image is 1. That’s not always a valid assumption. I’d grab the cgImage and use its width and height.
Even if you have only three components, you still need to use 4 bytes per pixel.
Thus:
guard
let photo = UIImage(named: "myphoto.jpg”),
let cgImage = photo.cgImage
else { return }
let bytesPerPixels = 4
let width = cgImage.width
let height = cgImage.height
let bitsPerComponent: Int = 8
let bytesPerRow = bytesPerPixels * width
let totalPixels = width * height
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedFirst.rawValue | CGBitmapInfo.byteOrder32Little.rawValue).rawValue
let colorSpace = CGColorSpaceCreateDeviceRGB()
guard
let ctx = CGContext(data: nil, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo),
let data = ctx.data
else { return }
ctx.draw(cgImage, in: CGRect(x: 0, y: 0, width: width, height: height))
let pointer = data.bindMemory(to: UInt32.self, capacity: totalPixels)
let pixels = UnsafeMutableBufferPointer(start: pointer, count: totalPixels)
for p in pixels {
print(String(p, radix: 16), Date())
}
You need to draw the image into the context.
ctx?.draw(photo.cgImage!, in: CGRect(origin: .zero, size: photo.size))
Add that just after creating the CGContext.
What I'm trying to do in Swift is merge two images together, the images I'm merging together is me dragging one image on top of another image with touch gestures. I get the images to composite, BUT the image I dragged on top of the main image does not keep it's position. How do I get it to stay where I placed it for the composite?
Here's my code:
extension CIHHatSelectionViewController{
// Return composite image of image2 overlayed on image1
//
func compositeImage(_ image1: UIImage, image2: UIImage, drawText: String, imageView1: CGPoint, imageView2:CGRect) -> UIImage {
let catPos = (image1.size.height - imageView2.origin.y) - imageView2.height
let bounds1 = CGRect(x: 0, y: 0, width: image1.size.width, height: image1.size.height)
let bounds2 = CGRect(x:imageView2.origin.x, y:catPos, width:imageView2.size.width, height:imageView2.size.height)
_ = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedFirst.rawValue)
let ctx = CGContext(data: nil,
width: image1.cgImage!.width,
height: image1.cgImage!.height,
bitsPerComponent: image1.cgImage!.bitsPerComponent,
bytesPerRow: image1.cgImage!.bytesPerRow,
space: image1.cgImage!.colorSpace!,
bitmapInfo: bitmapInfo.rawValue)!
ctx.draw(image1.cgImage!, in: bounds1, byTiling: false)
ctx.setBlendMode(.normal) // one image over the other
ctx.draw(image2.cgImage!, in: bounds2, byTiling: false)
let finalImage = textToImage(drawText, inImage: UIImage(cgImage: ctx.makeImage()!), atPoint: imageView1)
return finalImage
}
I would like to get the RGB (actually, the image provided has been grey-scaled, so grey-scale information would be sufficient) values of the individual pixels of a CIImage.
I currently have the following code:
//
// Conversion of CIImage to CGImage
//
func convertCIImageToCGImage(inputImage: CIImage) -> CGImage! {
return CIContext(options: nil).createCGImage(inputImage, fromRect: inputImage.extent)
}
process(image: CGImage) {
let img=convertCIImageToCGImage(image)
// Set image width, height
width = CGImageGetWidth(img)
height = CGImageGetHeight(img)
let colorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedFirst.rawValue)
// Create the bitmap context (ARGB)
context = CGBitmapContextCreate(nil, width, height, 8, bitmapBytesPerRow, colorSpace, bitmapInfo.rawValue)!
// draw the image onto the context
let rect = CGRect(x: 0, y: 0, width: width, height: height)
CGContextDrawImage(context, rect, img)
let uncasted_data = CGBitmapContextGetData(context)
data = UnsafePointer<UInt8>(uncasted_data)
...
}
I then access the individual Pixels using the data variable. I realise that most of the time of this function is spent in
CGContextDrawImage(context, rect, img)
Is there another way of accessing the bitmap of a CIImage or CGImage?
It is commonly required to get the pixel data from an image or reconstruct that image from pixel data. How can I take an image, convert it to an array of pixel values and then reconstruct it using the pixel array in Swift using CoreGraphics?
The quality of the answers to this question have been all over the place so I'd like a canonical answer.
Get pixel values as an array
This function can easily be extended to a color image. For simplicity I'm using grayscale, but I have commented the changes to get RGB.
func pixelValuesFromImage(imageRef: CGImage?) -> (pixelValues: [UInt8]?, width: Int, height: Int)
{
var width = 0
var height = 0
var pixelValues: [UInt8]?
if let imageRef = imageRef {
let totalBytes = imageRef.width * imageRef.height
let colorSpace = CGColorSpaceCreateDeviceGray()
pixelValues = [UInt8](repeating: 0, count: totalBytes)
pixelValues?.withUnsafeMutableBytes({
width = imageRef.width
height = imageRef.height
let contextRef = CGContext(data: $0.baseAddress, width: width, height: height, bitsPerComponent: 8, bytesPerRow: width, space: colorSpace, bitmapInfo: 0)
let drawRect = CGRect(x: 0.0, y:0.0, width: CGFloat(width), height: CGFloat(height))
contextRef?.draw(imageRef, in: drawRect)
})
}
return (pixelValues, width, height)
}
Get image from pixel values
I reconstruct an image, in this case grayscale 8-bits per pixel, back into a CGImage.
func imageFromPixelValues(pixelValues: [UInt8]?, width: Int, height: Int) -> CGImage?
{
var imageRef: CGImage?
if let pixelValues = pixelValues {
let bitsPerComponent = 8
let bytesPerPixel = 1
let bitsPerPixel = bytesPerPixel * bitsPerComponent
let bytesPerRow = bytesPerPixel * width
let totalBytes = width * height
let unusedCallback: CGDataProviderReleaseDataCallback = { optionalPointer, pointer, valueInt in }
let providerRef = CGDataProvider(dataInfo: nil, data: pixelValues, size: totalBytes, releaseData: unusedCallback)
let bitmapInfo: CGBitmapInfo = [CGBitmapInfo(rawValue: CGImageAlphaInfo.none.rawValue), CGBitmapInfo(rawValue: CGImageByteOrderInfo.orderDefault.rawValue)]
imageRef = CGImage(width: width,
height: height,
bitsPerComponent: bitsPerComponent,
bitsPerPixel: bitsPerPixel,
bytesPerRow: bytesPerRow,
space: CGColorSpaceCreateDeviceGray(),
bitmapInfo: bitmapInfo,
provider: providerRef!,
decode: nil,
shouldInterpolate: false,
intent: .defaultIntent)
}
return imageRef
}
Demoing the code in a Playground
You'll need an image copied into the Playground's Resources folder and then change the filename and extension below to match. The result on the last line is a UIImage constructed from the CGImage.
import Foundation
import CoreGraphics
import UIKit
import PlaygroundSupport
let URL = playgroundSharedDataDirectory.appendingPathComponent("zebra.jpg")
print("URL \(URL)")
var image: UIImage? = nil
if FileManager().fileExists(atPath: URL.path) {
do {
try NSData(contentsOf: URL, options: .mappedIfSafe)
} catch let error as NSError {
print ("Error: \(error.localizedDescription)")
}
image = UIImage(contentsOfFile: URL.path)
} else {
print("File not found")
}
let (intensityValues, width, height) = pixelValuesFromImage(imageRef: image?.cgImage)
let roundTrippedImage = imageFromPixelValues(pixelValues: intensityValues, width: width, height: height)
let zebra = UIImage(cgImage: roundTrippedImage!)
I was having trouble getting Cameron's code above to work, so I wanted to test another method. I found Vacawama's code, which relies on ARGB pixels. You can use that solution and convert each grayscale value to an ARGB value by simply mapping on each value:
/// Assuming grayscale pixels contains floats in the range 0...1
let grayscalePixels: [Float] = ...
let pixels = grayscalePixels.map {
let intensity = UInt8(round($0 / Float(UInt8.max)))
return PixelData(a: UInt8.max, r: intensity, g: intensity, b: intensity)
}
let image = UIImage(pixels: pixels, width: width, height: height)