How to select part of an image dynamically?

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In my App, I load an image. Since this image contains some useless information on its top and bottom area, I want to re-draw the image and only take its center part of the original (like Paint's Select Tool). Is it possible? Thanks.

What I have tried:

How to select part of an image dynamically?

Posted 6-Feb-19 7:50am

s yu

Updated 6-Feb-19 8:01am

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OriginalGriff · Answer 1 · 2019-02-06T08:01:00

Solution 1

Create a new Bitmap the correct size, and use DrawImage to draw only the required area into it: Graphics.DrawImage Method (System.Drawing) | Microsoft Docs[^] The first overload should do it: Graphics.DrawImage Method (System.Drawing) | Microsoft Docs[^]

Posted 6-Feb-19 8:01am

OriginalGriff

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s yu 7-Feb-19 11:18am

Thanks for your response. Per your answer, I did the following

SaveImageFile(image, "Temp");
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(image);
RectangleF rect = new RectangleF(0,25,100,100);
g.DrawImage(image, 25F, 25F, rect, GraphicsUnit.Point);
g.DrawImage(image, rect);
Bitmap bmp = new Bitmap(100, 100, g);
SaveImageFile(bmp, "Temp_");

I saved both images. The 1st one is fine, but the 2nd one is nothing but displays a black box. What wrong in code? Thanks if you can help.

OriginalGriff 7-Feb-19 14:05pm

"Create a new Bitmap the correct size" - did you do that? No.
"use DrawImage to draw only the required area into it" - did you do that? No, you drew onto the image you are drawing from ... twice.
Then you create a new bitmap, draw nothing on it, and save it ...

Please, read what I said, and try to think before you rush into code. :laugh: