How to change color of Image at runtime

Question

I would like to know is there any way by which we can change the Image color at runtime. for e.g lets say I am having a JPG bind to an Image control of ASP.Net. Next I am having a dropdown List which gives me the various color option like red,gree,etc. I would now like to change the color of the Image to the one selected in the droprdown List.

You'll need to say more about what you're doing. "The image" doesn't mean anything to anyone else. — Will Dean, Dec 20 '08 at 08:56
Do you have a picture you want to manipulate, or is it because you need illustrate the selected color? What im trying to figure out is, if you want to make a picture of, lets say a dog, more greener when green is selected. Or you want to just show a picture of a green color. — Tom Jelen, Dec 20 '08 at 13:25
It sounds to me like the OP wants to change the color of an "image" client-side. Could you better define what "image" means in this context? Do you mean the JPG, a border/background to the JPG? — Russ Cam, Jun 02 '09 at 11:16

score 12 · Answer 1 · answered Dec 20 '08 at 13:17

12

Here is a code sample that loads a JPEG, changes any red pixels in the image to blue, and then displays the bitmap in a picture box:

Bitmap bmp = (Bitmap)Bitmap.FromFile("image.jpg");
for (int x = 0; x < bmp.Width; x++)
{
    for (int y = 0; y < bmp.Height; y++)
    {
        if (bmp.GetPixel(x, y) == Color.Red)
        {
            bmp.SetPixel(x, y, Color.Blue);
        }
    }
}
pictureBox1.Image = bmp;

Warning: GetPixel and SetPixel are incredibly slow. If your images are large and/or performance is an issue, there is a much faster way to read and write pixels in .NET, but it's a little bit more work.

answered Dec 20 '08 at 13:17

MusiGenesis

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Comparing the GetPixel result with a Color doesn't always work. You should compare their ToArbg() results as shown here: http://stackoverflow.com/questions/7464994/how-to-compare-a-color-by-the-getpixel-method-and-a-color-passed-in-a-method-lik – FoppyOmega Feb 06 '13 at 18:08
Actually, I'm not sure my code would *ever* work. I think even if the bitmap's pixel color has the exact same ARGB values as Color.Red, it still will not be equivalent to Color.Red. – MusiGenesis Feb 06 '13 at 19:01

score 0 · Answer 2 · answered Aug 17 '13 at 19:37

You also try this for web (asp.net) , you can ignore the logic but can see what getpixel & setpixel doing

 public string FileUpload( HttpPostedFileBase file )
  {
     Bitmap bmp = new Bitmap(file.InputStream);
     string valid = "";

     for(int i = 0; i < bmp.Width; i++) {
        for(int j = 0; j < bmp.Height; j++) {
           if(bmp.GetPixel(i , j).B < 20) {
              if(bmp.GetPixel(i , j).B == bmp.GetPixel(i , j).G &&
                 bmp.GetPixel(i , j).B == bmp.GetPixel(i , j).R) {
                 valid = valid + bmp.GetPixel(i , j). + "<br/>";
                 bmp.SetPixel(i , j , Color.DarkGreen);
              }
           }
        }
     }

     SaveImage(bmp);

     return valid;
  }

  private void SaveImage( Bitmap newbmp )
  {
     string path = Path.Combine(Server.MapPath("~/Images") , "ScaledImage.jpeg");
     newbmp.Save(path , System.Drawing.Imaging.ImageFormat.Jpeg);
  }

score -1 · Answer 3 · edited Jan 17 '13 at 15:22

I am also facing trouble to under this question. after that based on the some information. I wrote the code manually.Now it works well. If you want to check.you can use it.

code for change the background image during runtime in C#.net

you can use simply this code. That is, ==>

string str; 
OpenFileDialog od = new OpenFileDialog(); 
if (od.ShowDialog() == DialogResult.OK) 
{ 
    str = od.FileName;
    this.BackgroundImage=Image.FromFile(str); 
}

How to change color of Image at runtime

3 Answers3

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