下面的代码尝试将像素设置为离线位图并将该位图绘制到屏幕上。不幸的是,它崩溃了。
import UIKit
class GameView: UIView {
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
override init(frame: CGRect) {
super.init(frame: frame)
}
func createBitmapContext(pixelsWide: Int, _ pixelsHigh: Int) -> CGContextRef? {
let bytesPerPixel = 4
let bytesPerRow = bytesPerPixel * pixelsWide
let bitsPerComponent = 8
let byteCount = (bytesPerRow * pixelsHigh)
let colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB)
let pixels = UnsafeMutablePointer<CUnsignedChar>.alloc(byteCount)
if pixels == nil {
return nil
}
let bitmapInfo = CGImageAlphaInfo.PremultipliedFirst.rawValue | CGBitmapInfo.ByteOrder32Little.rawValue
let context = CGBitmapContextCreate(pixels, pixelsWide, pixelsHigh, bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo)
return context
}
override func drawRect(rect: CGRect) {
let width = 200
let height = 300
let boundingBox = CGRectMake(0, 0, CGFloat(width), CGFloat(height))
let context = createBitmapContext(width, height)
let data = CGBitmapContextGetData(context)
var currentPixel: [UInt32] = unsafeBitCast(data, [UInt32].self)
var n = 0
for var j = 0; j < height; j++ {
for var i = 0; i < width; i++ {
currentPixel[n++] = 0
}
}
let image = CGBitmapContextCreateImage(context!)
CGContextDrawImage(context!, boundingBox, image)
}
}
需要进行一些更改。
1、内存溢出导致崩溃。
2. 您正在从新创建的上下文创建图像并写入相同的上下文而不是当前的绘图上下文。
使用这个修改后的drawRect函数:
override func drawRect(rect: CGRect) {
let width = 200
let height = 300
let boundingBox = CGRectMake(0, 0, CGFloat(width), CGFloat(height))
let context = createBitmapContext(width, height)
let data = CGBitmapContextGetData(context)
let pixels = UnsafeMutablePointer<CUnsignedChar>(data)
var n = 0
for var j = 0; j < height; j++ {
for var i = 0; i < width; i++ {
pixels[n++] = 0 //B
pixels[n++] = 255 //G
pixels[n++] = 0 //R
pixels[n++] = 255 //A
}
}
let image = CGBitmapContextCreateImage(context!)
if let currentContext: CGContext! = UIGraphicsGetCurrentContext() {
UIImagePNGRepresentation(UIImage(CGImage:image!))?.writeToFile("/Users/admin/Desktop/aaaaa.png", atomically: true)
CGContextDrawImage(currentContext, boundingBox, image)
}
}
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