如何使用CGContext获得像素的RGB值? [英] How do I get the RGB Value of a pixel using CGContext?

问题描述

我正在尝试通过更改像素来编辑图像.

我有以下代码:

  let imageRect = CGRectMake(0，0，self.image.image！.size.width，self.image.image！.size.height)UIGraphicsBeginImageContext(self.image.image！.size)让上下文= UIGraphicsGetCurrentContext()CGContextSaveGState(上下文)CGContextDrawImage(context，imageRect，self.image.image！.CGImage)对于x in 0 ... Int(self.image.image！.size.width){y in 0 ... Int(self.image.image！.size.height){var red = 0如果y％2 == 0 {红色= 255}CGContextSetRGBFillColor(context，CGFloat(red/255)，0.5，0.5，1)CGContextFillRect(上下文，CGRectMake(CGFloat(x)，CGFloat(y)，1，1))}}CGContextRestoreGState(上下文)self.image.image = UIGraphicsGetImageFromCurrentImageContext() 

我正在遍历所有像素并更改每个像素的值，然后将其转换回图像.我想要做的就是以某种方式获取当前像素的值(在y-for循环中)并对该数据进行一些处理.我没有在互联网上找到有关此特定问题的任何信息.

解决方案

好吧，我想我有一个应该可以在Swift 2中使用的解决方案.

对于以下UIColor扩展，请

对此:

这对我在操场上有效-您所需要做的就是将其复制并粘贴到操场上以查看结果:

 //:游乐场-名词:人们可以玩耍的地方导入UIKit导入XCPlayground扩展名CALayer {func colorOfPoint(point:CGPoint)->UIColor{var pixel:[CUnsignedChar] = [0,0,0,0]让colorSpace = CGColorSpaceCreateDeviceRGB()让bitmapInfo = CGBitmapInfo(rawValue:CGImageAlphaInfo.PremultipliedLast.rawValue)let context = CGBitmapContextCreate(& pixel，1，1，8，4，colorSpace，bitmapInfo.rawValue)CGContextTranslateCTM(上下文，-point.x，-point.y)self.renderInContext(上下文！)让红色:CGFloat = CGFloat(pixel [0])/255.0让绿色:CGFloat = CGFloat(pixel [1])/255.0让蓝色:CGFloat = CGFloat(pixel [2])/255.0令alpha:CGFloat = CGFloat(pixel [3])/255.0//println(点颜色-红色:\(红色)绿色:\(绿色)蓝色:\(蓝色)")let color = UIColor(红色:红色，绿色:绿色，蓝色:蓝色，alpha:alpha)返回颜色}}扩展UIColor {var组件:(红色:CGFloat，绿色:CGFloat，蓝色:CGFloat，alpha:CGFloat){var r:CGFloat = 0var g:CGFloat = 0var b:CGFloat = 0var a:CGFloat = 0getRed(& r，绿色:& g，蓝色:& b，alpha:& a)返回(r，g，b，a)}}//获取我们可以处理的图像var imageFromURL = UIImage(data:NSData(contentsOfURL:NSURL(string:"https://www.gravatar.com/avatar/ba4178644a33a51e928ffd820269347c?s=328&d=identicon&r=PG&f=1")！)！)//仅使用该图像的一小部分-50 x 50平方let imageSliceArea = CGRectMake(0，0，50，50);让imageSlice = CGImageCreateWithImageInRect(imageFromURL?.CGImage，imageSliceArea);//我们将处理这张图片var image = UIImage(CGImage:imageSlice！)让imageView = UIImageView(image:image)//测试点(0,0)上的扩展-返回r 0.541 g 0.78 b 0.227 a 1.0var pointColor = imageView.layer.colorOfPoint(CGPoint(x:0，y:0))让imageRect = CGRectMake(0，0，image.size.width，image.size.height)UIGraphicsBeginImageContext(image.size)让上下文= UIGraphicsGetCurrentContext()CGContextSaveGState(上下文)CGContextDrawImage(context，imageRect，image.CGImage)对于x in 0 ... Int(image.size.width){y in 0 ... Int(image.size.height){var pointColor = imageView.layer.colorOfPoint(CGPoint(x:x，y:y))//我在这里运用了自己的创造力-将其更改为您想要的任何逻辑如果y％2 == 0 {CGContextSetRGBFillColor(context，pointColor.components.red，0.5，0.5，1)}别的 {CGContextSetRGBFillColor(context，255，0.5，0.5，1)}CGContextFillRect(上下文，CGRectMake(CGFloat(x)，CGFloat(y)，1，1))}}CGContextRestoreGState(上下文)图片= UIGraphicsGetImageFromCurrentImageContext() 

我希望这对您有用.我玩这个很开心！

I'm trying to edit images by changing the pixels.

I have the following code:

    let imageRect = CGRectMake(0, 0, self.image.image!.size.width, self.image.image!.size.height)

    UIGraphicsBeginImageContext(self.image.image!.size)
    let context = UIGraphicsGetCurrentContext()

    CGContextSaveGState(context)
    CGContextDrawImage(context, imageRect, self.image.image!.CGImage)

    for x in 0...Int(self.image.image!.size.width) {
        for y in 0...Int(self.image.image!.size.height) {
            var red = 0
            if y % 2 == 0 {
                red = 255
            }

            CGContextSetRGBFillColor(context, CGFloat(red/255), 0.5, 0.5, 1)
            CGContextFillRect(context, CGRectMake(CGFloat(x), CGFloat(y), 1, 1))
        }
    }
    CGContextRestoreGState(context)
    self.image.image = UIGraphicsGetImageFromCurrentImageContext()

I'm looping through all the pixels and changing the value of the each pixel, then converting it back to an image. Want I want to do is somehow get the value of the current pixel (in the y-for-loop) and do something with that data. I have not found anything on the internet about this particular problem.

解决方案

Ok, I think I have a solution that should work for you in Swift 2.

Credit goes to this answer for the UIColor extension below.

Since I needed an image to test this on I chose a slice (50 x 50 - top left corner) of your gravatar...

So the code below converts this:

To this:

This works for me in a playground - all you should have to do is copy and paste into a playground to see the result:

//: Playground - noun: a place where people can play

import UIKit
import XCPlayground

extension CALayer {

    func colorOfPoint(point:CGPoint) -> UIColor
    {
        var pixel:[CUnsignedChar] = [0,0,0,0]

        let colorSpace = CGColorSpaceCreateDeviceRGB()
        let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedLast.rawValue)

        let context = CGBitmapContextCreate(&pixel, 1, 1, 8, 4, colorSpace,bitmapInfo.rawValue)

        CGContextTranslateCTM(context, -point.x, -point.y)

        self.renderInContext(context!)

        let red:CGFloat = CGFloat(pixel[0])/255.0
        let green:CGFloat = CGFloat(pixel[1])/255.0
        let blue:CGFloat = CGFloat(pixel[2])/255.0
        let alpha:CGFloat = CGFloat(pixel[3])/255.0

        //println("point color - red:\(red) green:\(green) blue:\(blue)")

        let color = UIColor(red:red, green: green, blue:blue, alpha:alpha)

        return color
    }
}

extension UIColor {
    var components:(red: CGFloat, green: CGFloat, blue: CGFloat, alpha: CGFloat) {
        var r:CGFloat = 0
        var g:CGFloat = 0
        var b:CGFloat = 0
        var a:CGFloat = 0
        getRed(&r, green: &g, blue: &b, alpha: &a)
        return (r,g,b,a)
    }
}


//get an image we can work on
var imageFromURL = UIImage(data: NSData(contentsOfURL: NSURL(string:"https://www.gravatar.com/avatar/ba4178644a33a51e928ffd820269347c?s=328&d=identicon&r=PG&f=1")!)!)
//only use a small area of that image - 50 x 50 square
let imageSliceArea = CGRectMake(0, 0, 50, 50);
let imageSlice  = CGImageCreateWithImageInRect(imageFromURL?.CGImage, imageSliceArea);
//we'll work on this image
var image = UIImage(CGImage: imageSlice!)


let imageView = UIImageView(image: image)
//test out the extension above on the point (0,0) - returns r 0.541 g 0.78 b 0.227 a 1.0
var pointColor = imageView.layer.colorOfPoint(CGPoint(x: 0, y: 0))



let imageRect = CGRectMake(0, 0, image.size.width, image.size.height)

UIGraphicsBeginImageContext(image.size)
let context = UIGraphicsGetCurrentContext()

CGContextSaveGState(context)
CGContextDrawImage(context, imageRect, image.CGImage)

for x in 0...Int(image.size.width) {
    for y in 0...Int(image.size.height) {
        var pointColor = imageView.layer.colorOfPoint(CGPoint(x: x, y: y))
        //I used my own creativity here - change this to whatever logic you want
        if y % 2 == 0 {
            CGContextSetRGBFillColor(context, pointColor.components.red , 0.5, 0.5, 1)
        }
        else {
            CGContextSetRGBFillColor(context, 255, 0.5, 0.5, 1)
        }

        CGContextFillRect(context, CGRectMake(CGFloat(x), CGFloat(y), 1, 1))
    }
}
CGContextRestoreGState(context)
image = UIGraphicsGetImageFromCurrentImageContext()

I hope this works for you. I had fun playing around with this!

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