回复:迅速从UIImage/CGImage获取像素数据作为数组

问题描述

限时删除！！

此代码适用于我(Swift 2游乐场)灰度，并加载彩色.BMP图像...

This code works for me (Swift 2 playground) in Gray scale, loading a colour .BMP image...

从UIImage/CGImage获取像素数据作为数组迅速

...但是如果我将bytesPerPixel更改为3(或4)并使用

... but if I change bytesPerPixel to 3 (or 4) and use

let colorSpace = CGColorSpaceCreateDeviceRGB()

...代码仍然可以正常运行，但是像素值全为零.关于如何解决该问题的任何建议?

...the code still runs with no errors, but pixel values are all zeros. Any suggestions as to how to fix that?

推荐答案

您可能忘记了CGImageAlphaInfo参数.对于彩色图像，如果假设bytesPerPixel为4，则在创建上下文时需要设置RGBA(或ARGB).以下是不具有alpha通道的RGBA的示例.

You probably forgot the CGImageAlphaInfo parameter. For color images, if you assume bytesPerPixel to be 4, you need to set either RGBA (or ARGB) when creating the context. Following is an example for RGBA without the alpha channel.

// RGBA format
let ctx = CGBitmapContextCreate(&data, pixelsWide, pixelsHigh, 8,
    bitmapBytesPerRow, colorSpace, CGImageAlphaInfo.NoneSkipLast.rawValue)

根据文档，您具有以下选项:

According to the documentation, you have these options:

enum CGImageAlphaInfo : UInt32 {
    case None
    case PremultipliedLast
    case PremultipliedFirst
    case Last
    case First
    case NoneSkipLast
    case NoneSkipFirst
    case Only
}

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