e.Graphics.DrawImage（）反向 [英] e.Graphics.DrawImage() in reverse

问题描述

嘿伙计们



我这样做了：

Hey guys

I have done this:

Dim ShouldPaintImage2 as boolean=true
Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
       e.Graphics.DrawImage(My.Resources.image1, 20, 20)
if ShouldPaintImage2=true then
[remove old graphic]
 e.Graphics.DrawImage(My.Resources.image2, 20, 20)
End Sub

是否可以删除 仅图像 的图形，以便将图像更改为图像2？



谢谢

Is it possible to remove only the graphic of image1 so i can change the image to image2?

Thanks

推荐答案

当然可以。您需要了解您正在使用的 OnPaint 是否在Windows WM_PAINT 消息上调用，您的UI收到每个失效：

http://msdn.microsoft.com/en -us / library / 598t492a.aspx [ ^ ]。



请查看我过去的答案：

mdi子窗体之间的绘制线 [ ^ ]，

在面板上捕获图纸 [ ^ ]，

什么样的俏皮方法是Paint？ （DataGridViewImageCell.Paint（...）） [ ^ ]，

如何加速我的vb.net应用程序？ [ ^ ]。



也就是说，你只需要这样：绘制不是固定的图像，而是绘制可变图像/位图参考。引用 Image ，例如，您的表单类的实例字段;让我们说，它的名字是 MyImage 。那么 DrawImage 的行应该更改为 e.Graphics.DrawImage（MyImage ...）。



现在，切换图像的过程看起来像

Yes of course. You need to understand that OnPaint, which you are correctly using, is called on the Windows WM_PAINT messages, which your UI receives on each invalidation:
http://msdn.microsoft.com/en-us/library/598t492a.aspx[^].

Please see my past answers:
Drawing Lines between mdi child forms[^],
capture the drawing on a panel[^],
What kind of playful method is Paint? (DataGridViewImageCell.Paint(...))[^],
How to speed up my vb.net application?[^].

That said, all you need is this: Draw not a fixed image, but a variable image/bitmap reference. Make a reference to Image an instance field of, say, your form class; let''s say, its name is MyImage. Then your line with DrawImage should be changes to e.Graphics.DrawImage(MyImage ...).

Now, the procedure of "switching the image" will look like

MyImage = ' different reference, ether image1 or image2...
self.Invalidate(); ' this will eventually cause re-painting
' here, "self" is your control, of the class where you override OnPaint;
' it could be your form or whatever control it is...

你明白了吗？

-SA

我想你以错误的方式解决这个问题，如果情况确实如此，那么首先不把它绘制起来会更有意义吗？即：

I think you''re going about this the wrong way, wouldn''t it make more sense to just not draw it in the first place if that''s the case? i.e.:

Dim ShouldPaintImage2 as boolean=true
Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
    If ShouldPaintImage2=true Then
        e.Graphics.DrawImage(My.Resources.image2, 20, 20)
    Else
        e.Graphics.DrawImage(My.Resources.image1, 20, 20)
    End If
End Sub

（对不起，如果这不是完美的话正确的语法，我的VB.Net非常生疏）



否则，据我所知，你不能删除一个特定的对象，如果你的真实代码更复杂，清除图形，然后使用image2而不是image1重绘整个图形。

(Sorry if this isn''t perfectly correct syntax, my VB.Net is very rusty)

Otherwise, to my knowledge you can''t erase a specific object, if your real code is more complicated, clear the drawing, then redraw the whole thing, using image2 instead of image1.

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