C＃从System.Drawing.Bitmap高效地获取像素数据 [英] C# Getting the pixel data efficiently from System.Drawing.Bitmap

问题描述

我有几个硬盘（〜2GB）生24 bpp的RGB文件。
现在我想找回它的一部分，并将其扩展到所需的大小。结果
（唯一允许的尺度是1，1/2，1/4，1/8，... 1/256）

I have several (~2GB) raw 24bpp RGB files on HDD. Now I want to retrieve a portion of it and scale it to the desired size.
(The only scales allowed are 1, 1/2, 1/4, 1/8, ..., 1/256)

所以我目前正在读从感兴趣的矩形每一行到一个数组，这让我有正确的高度，但宽度不正确的位图。

So I'm currently reading every line from the rectangle of interest into an array, which leaves me with a bitmap which has correct height but wrong width.

作为下一步我创建的新创建的数组的位图。结果
这是通过使用指针，所以没有涉及数据的复制完成。结果
接下来，我呼吁位图，它创建一个具有正确尺寸的新位图GetThumbnailImage。

As the next step I'm creating a Bitmap from the newly created array.
This is done with by using a pointer so there is no copying of data involved.
Next I'm calling GetThumbnailImage on the Bitmap, which creates a new bitmap with the correct dimensions.

现在我想新创建位图返回原始像素数据（一个字节数组）。
但要做到这一点，我目前使用拷贝到LockBits新的数组中的数据。

Now I want to return the raw pixel data (as a byte array) of the newly created bitmap. But to achieve that I'm currently copying the data using LockBits into a new array.

所以我的问题是：是否有一种方式来获得从位图成字节数组的像素数据，而不将其复制

是这样的：

var bitmapData = scaledBitmap.LockBits(...)
byte[] rawBitmapData = (byte[])bitmapData.Scan0.ToPointer()
scaledBitmap.UnlockBits(bitmapData)
return rawBitmapData 

我很清楚，这是不行的，这只是一个例子，我基本上要达到的。

I'm well aware that this doesn't work, it is just an example to what I basically want to achieve.

推荐答案

我觉得这是你最好的选择。

I think this is your best bet.

var bitmapData = scaledBitmap.LockBits(...);
var length = bitmapData.Stride * bitmapData.Height;

byte[] bytes = new byte[length];

// Copy bitmap to byte[]
Marshal.Copy(bitmapData.Scan0, bytes, 0, length);
scaledBitmap.UnlockBits(bitmapData);

您必须复制它，如果你想围绕一个字节一通[]。

You have to copy it, if you want a pass around a byte[].

您不必删除已分配的字节数，你只需要它实现IDisposable完成后丢弃原Bitmap对象。

You don't have to delete the bytes that were allocated, you just need to Dispose of the original Bitmap object when done as it implements IDisposable.

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