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?
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 would like to find the grayscale value of a grayscale UIImage at a given CGPoint as well as doing so when the UIImage has been zoomed and/or panned.
So far I've been able to extract the grayscale values of my entire image using CGContext then finding the grayscale value at point (x,y) in a 1D-array of those grayscale values using the index given by index = x*(width of image) + y. However, I'm unsure how to proceed once I have zoomed in on my image and/or panned it once zoomed.
//Converts image to list of grayscale values
func pixelValues(fromCGImage imageRef: CGImage?) -> (pixelValues: [UInt16]?, width: Int, height: Int)
{
var width = 0
var height = 0
var pixelValues: [UInt16]?
if let imageRef = imageRef {
width = imageRef.width
height = imageRef.height
let bitsPerComponent = imageRef.bitsPerComponent
let bytesPerRow = imageRef.bytesPerRow
let totalBytes = height * width
let colorSpace = CGColorSpaceCreateDeviceGray()
var intensities = [UInt16](repeating: 0, count: totalBytes)
let contextRef = CGContext(data: &intensities, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: 0)
contextRef?.draw(imageRef, in: CGRect(x: 0.0, y: 0.0, width: CGFloat(width), height: CGFloat(height)))
pixelValues = intensities
}
return (pixelValues ,width, height)
}
//Returns grayscale value of image at pixel (x,y)
func getGrayValue(pixelValues: [UInt16], width: Int, x: Int, y: Int) -> UInt16 {
let i = x*width + y
return pixelValues[i]
}
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.)
I have a gray scale image of depth data that has been upsampled from its original resolution. I'm stuck as to how I can convert the pixel values of the upscaled depth image (r,g,b) to a float.
Is there a way to convert the level of whiteness of a pixel a float value?
Is there anyway I could convert the CVPixelBufferFormatTypes of the CVPixelBuffer associated with the image?
Said another way, is there a way to convert the pixel buffer of a gray scale image into CVpixelbuffer containing disparity floats?
I use the following code to extract the cvpixelbuffer from a cgimage representation of the upsampled depth data:-
func pixelBuffer() -> CVPixelBuffer? {
let frameSize = CGSize(width: self.width, height: self.height)
//COLOR IS BGRA
var pixelBuffer:CVPixelBuffer? = nil
let status = CVPixelBufferCreate(kCFAllocatorDefault, Int(frameSize.width), Int(frameSize.height), kCVPixelFormatType_32BGRA , nil, &pixelBuffer)
if status != kCVReturnSuccess {
return nil
}
CVPixelBufferLockBaseAddress(pixelBuffer!, CVPixelBufferLockFlags.init(rawValue: 0))
let data = CVPixelBufferGetBaseAddress(pixelBuffer!)
let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(rawValue: CGBitmapInfo.byteOrder32Big.rawValue | CGImageAlphaInfo.premultipliedFirst.rawValue)
let context = CGContext(data: data, width: Int(frameSize.width), height: Int(frameSize.height), bitsPerComponent: 8, bytesPerRow: CVPixelBufferGetBytesPerRow(pixelBuffer!), space: rgbColorSpace, bitmapInfo: bitmapInfo.rawValue)
context?.draw(self, in: CGRect(x: 0, y: 0, width: self.width, height: self.height))
CVPixelBufferUnlockBaseAddress(pixelBuffer!, CVPixelBufferLockFlags(rawValue: 0))
return pixelBuffer
}
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)