F#如何从修改后的bytearray []中保存图像？

Question

到目前为止，我已经得到了什么，从中学习

https://web.archive.org/web/20141229164101/http://bobpowell.net/lockingbits.aspx

https://stackoverflow.com/a/4619004/3487239

https://stackoverflow.com/a/22855181/3487239

open System.Drawing
open System.Drawing.Imaging

let cat = new Bitmap("cat.jpg") // original image of cat

let pixels (image:Bitmap) = // BitLocking and Unlocking an Image
    let Width = image.Width
    let Height = image.Height
    let rect = new Rectangle(0,0,Width,Height)

    // Lock the image for access
    let data = image.LockBits(rect, ImageLockMode.ReadOnly, image.PixelFormat)

    // Copy the data
    let ptr = data.Scan0
    let stride = data.Stride
    let bytes = stride * data.Height
    let values : byte[] = Array.zeroCreate bytes
    System.Runtime.InteropServices.Marshal.Copy(ptr,values,0,bytes)
    let pixelSize = 4 // <-- calculate this from the PixelFormat
    
    // All the data has been inserted into byte[] values
    (*

       This block of code is where I go through the byte[] values from above
       to do all sorts of image manipulation eg. changing color of pixels etc
       Which I have completed, just need to save the image.

    *)

    // My Question
    (*
       In here, how to turn the modified byte[] values back to Bitmap before
       unlocking the bits?
    *)

    // Unlock the image
    image.UnlockBits(data)

pixels cat // modified version of the same image

到目前为止我已经尝试过，（新的内存流到新的位图，新的位图构造函数，然后是 bitmap.save 等等......）

https://stackoverflow.com/a/22890620/3487239

https://stackoverflow.com/a/3801289/3487239

代码使用上述方法编译，但它会创建同一图像的另一个副本，而不是所需的结果。

Answer 1

想通了，你执行以下操作：

// this is the first copy operation in your lock/unlock
{
.
.
.
System.Runtime.InteropServices.Marshal.Copy(ptr,values,0,bytes)
.
.
.
}
// you have to do lock/unlock again, this time with your modified byte array, copy again, rearrange the parameter this way
{
.
.
.
System.Runtime.InteropServices.Marshal.Copy(values,0,ptr,bytes)
.
.
.
}
// then save the bitmap with new directory/filename