Change pixel color in C #
Hi I am working on a program that reads a whole image and changes the color of the green line to a red line, for example I have this image 
and I want a C # program to get green pixels and convert them to red I tried this code: `
public Bitmap ReadImgPixel(Bitmap img)
{
Bitmap pic = new Bitmap(img,img.Width,img.Height);
int a1 = img.Width;
int a2 = img.Height;
System.Drawing.Color[,] pixels = new System.Drawing.Color[a1,a2];
for (int i = 0;i< img.Width ; i++)
{
for(int j=0; j < img.Height; j++)
{
System.Drawing.Color pxl = img.GetPixel(i, j);
if (pxl != System.Drawing.Color.White)
{
pic.SetPixel(i, j, System.Drawing.Color.Red);
}
}
}
return pic;
}
but as a result the whole image changed to red, how to fix it.
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Have you tried debugging (you could easily find out why all the pixels turned red)? Your whole picture turns red because the operator is if
always there true
.
The reason for this is because you are comparing structures. However, your pixel name
won't say White
(what you are comparing), but it will contain a string with hex
your color value (for example ffffff
). Therefore, he is never equal, because the objects are different. Therefore, since you want to know if the values are the same ARGB
, you must compare them.
Change your operator to this to compare values ARGB
:
if (pxl.ToArgb() != Color.White.ToArgb())
Also make sure you check Cody Gray's comment as your code is completely ineffective. If efficiency is important to you, try a different approach, but that is beyond the scope of this question.
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