GDI +：你怎么渲染图形对象在后台线程位图？ [英] GDI+: how do you render a Graphics object to a bitmap on a background thread?

问题描述

我想使用GDI +在后台线程渲染图像。我发现本例中如何旋转使用GDI +的图像的，这是我喜欢做的操作。

I'd like to use GDI+ to render an image on a background thread. I found this example on how to rotate an image using GDI+, which is the operation I'd like to do.

private void RotationMenu_Click(object sender, System.EventArgs e)
{
    Graphics g = this.CreateGraphics();
    g.Clear(this.BackColor);
    Bitmap curBitmap = new Bitmap(@"roses.jpg"); 
    g.DrawImage(curBitmap, 0, 0, 200, 200);  

    // Create a Matrix object, call its Rotate method,
    // and set it as Graphics.Transform
    Matrix X = new Matrix();
    X.Rotate(30);
    g.Transform = X;  

    // Draw image
    g.DrawImage(curBitmap, 
    new Rectangle(205, 0, 200, 200), 
        0, 0, curBitmap.Width, 
        curBitmap.Height, 
        GraphicsUnit.Pixel);  

    // Dispose of objects
    curBitmap.Dispose();
    g.Dispose(); 
} 

我的问题有两个部分：

My question has two parts:

1. 你会如何完成 this.CreateGraphics（）在后台线程？是否可以？我的理解是，一个UI对象是这个在这个例子中。所以，如果我在后台线程这样处理，我将如何创建一个图形对象？

1. How would you accomplish this.CreateGraphics() on a background thread? Is it possible? My understanding is that a UI object is this in this example. So if I'm doing this processing on a background thread, how would I create a graphics object?

我怎么会那么提取的Graphics对象，位图我使用的是一旦我做了处理？我一直没能找到该怎么做一个很好的例子。

How would I then extract a bitmap from the Graphics object I'm using once I'm done processing? I haven't been able to find a good example of how to do that.

另外：格式化代码样本时，如何添加换行符？如果有人可以给我留下了评论，解释说我会很感激。谢谢！

---

Also: when formatting a code sample, how do I add newlines? If someone could leave me a comment explaining that I'd really appreciate it. Thanks!

推荐答案

要绘制一个位图，你不希望创建一个图形对象的UI控件。创建使用 FromImage 方法的位图图形目标：

To draw on a bitmap you don't want to create a Graphics object for an UI control. You create a Graphics object for the bitmap using the FromImage method:

Graphics g = Graphics.FromImage(theImage);

A 图形对象不包含您绘制它的图形，而不是它只是借鉴其他画布，这通常是在屏幕的一个工具，但它也可以是一个位图对象。

A Graphics object doesn't contain the graphics that you draw to it, instead it's just a tool to draw on another canvas, which is usually the screen, but it can also be a Bitmap object.

所以，你不画，然后再提取位图，首先要创建位图，然后创建图形对象借鉴它：

So, you don't draw first and then extract the bitmap, you create the bitmap first, then create the Graphics object to draw on it:

Bitmap destination = new Bitmap(200, 200);
using (Graphics g = Graphics.FromImage(destination)) {
   Matrix rotation = new Matrix();
   rotation.Rotate(30);
   g.Transform = rotation;
   g.DrawImage(source, 0, 0, 200, 200);
}

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