C# Tutorial: Cropping images and bitmaps

[ArekBulski]

Introduction for curious people

I got a nice homework assignment from Siten, to make a program that crops images. It seemed easy at first, but then ...proven otherwise. Therefore let me show you some code that "cuts margins off images", or how Photoshop names it: crops images.

Cropping an image (or bitmap)

First of all, you can only crop a Bitmap class. If you have an Image class, you will have to transform it to a Bitmap object. This is my first code statement.

Bitmap croppedBitmap = new Bitmap(pictureBox1.Image); 

Cropping a Bitmap may seem hard to implement, probably because it is being done by cloning... yes, Clone() method takes optional arguments that can be smaller than original image. This is second code statement.

My margins are provided by NumericUpDown controls, therefore I had to convert them from double to integer, which adds these "(int)" explicit conversions.

croppedBitmap = croppedBitmap.Clone(
    new Rectangle(
        (int)LeftMargin.Value, (int)TopMargin.Value,
        (int)croppedBitmap.Width - (int)LeftMargin.Value - (int)RightMargin.Value,
        (int)croppedBitmap.Height - (int)TopMargin.Value - (int)BottomMargin.Value),
    System.Drawing.Imaging.PixelFormat.DontCare); 

To show the results, my cropped image is put back into picturebox1. This is third code statement.

pictureBox1.Image = croppedBitmap; 

Output to show that it works

Here are screenshots showing two subsequent cropping done on a picture made by NASA.



Code behind this prototype

You can open the whole solution and play with it as you want. Also you can run a compiled exe without using Visual Studio, just look into Bin\Release\ folder.

Solution code: Cropping Images Prototype.zip

With regards to Siten, my old friend...

[Jordan]

Short and sweet! Nice tutorial. +rep

[relapse]

I don't use C# but this seems really cool!

[ArekBulski]

Short and sweet! Nice tutorial. +rep

I don't use C# but this seems really cool!

Thank you, guys! I appreciate your comments. Relapse, I would be interested in getting some +rep, if you would like to give some. I am trying to get enough rep to earn a logo T-Shirt. But thank you anyways! Feels great to be seen as a good coder by others.

[relapse]

wtf is +rep?

[WingedPanther]

Click on the scales icon next to a post to indicate you think it was particularly good/helpful.

[Vswe]

relapse doesn't even have any reppower so it doesn't matter.

[ArekBulski]

relapse doesn't even have any reppower so it doesn't matter.

Uh-oh, I see. You are right there, his rep power is 0. But your rep power is... woow. Wanna use it?

[Vswe]

You know you only can receive 15+rep at the time?

[ArekBulski]

You know you only can receive 15+rep at the time?

I had no idea. Thanks for telling. But no rep... *sniff*