Convert an Image to Grayscale - C# : The Official Microsoft ASP.NET Forums

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Convert an Image to Grayscale - C#

Dec 30, 2012 07:06 PM|LINK

Hi there, I hope your help.

I need convert an color image to Grayscale with C#.

I tried this code but I have error, why?

thank you

CS1502: ConvertToGrayscale (System.Drawing.Bitmap) has some invalid arguments

    protected void Page_Load(object sender, EventArgs e)
    {

           .......

            string Img = "http://www.mywebpage.com/images/" + (Convert.ToString(dr1["myPicture"]);
            lblImage2.ImageUrl = ConvertToGrayscale(Img);

    }


    public Bitmap ConvertToGrayscale(Bitmap source)
    {
        Bitmap bm = new Bitmap(source.Width, source.Height);
        for (int y = 0; y < bm.Height; y++)
        {
            for (int x = 0; x < bm.Width; x++)
            {
                Color c = source.GetPixel(x, y);
                int luma = (int)(c.R * 0.3 + c.G * 0.59 + c.B * 0.11);
                bm.SetPixel(x, y, Color.FromArgb(luma, luma, luma));
            }
        }
        return bm;
    }

Moved by MetalAsp.Net on Dec 30, 2012 07:28 PM
Edited by cms9651 on Dec 31, 2012 08:10 AM

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Re: Convert an Image to Grayscale - C#

Dec 31, 2012 08:29 AM|LINK

I tried this, but I have error:
CS0117: 'System.Web.UI.WebControls.Image' does not contain a definition for 'Image'
Can you help me?

<asp:Image ID="lblImage2" runat="server" />


    protected void Page_Load(object sender, EventArgs e)
    {

         bitmapmakegrayscale(lblImage2.Image);
    }


    private void bitmapmakegrayscale(System.Drawing.Image imagei)
    {
        Bitmap image = imagei as Bitmap;
        Bitmap bp = new Bitmap(image.Width, image.Height);
        for (int i = 0; i < image.Width; i++)
        {
            for (int j = 0; j < image.Height; j++)
            {
                Color orgcol = image.GetPixel(i, j);
                int grayscale = (int)((orgcol.R * .3) + (orgcol.G * .59) + (orgcol.B * .11));
                Color newcol = Color.FromArgb(grayscale, grayscale, grayscale);
                bp.SetPixel(i, j, newcol);
            }
        }
        lblImage2.Image = bp;
    }

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Re: Convert an Image to Grayscale - C#

Dec 31, 2012 08:41 AM|LINK

Try the below code,

public Bitmap GrayScale(Bitmap Bmp)
{
int rgb;
Color c;

for (int y = 0; y < Bmp.Height; y++)
for (int x = 0; x < Bmp.Width; x++)
{
c = Bmp.GetPixel(x, y);
rgb = (int)((c.R + c.G + c.B) / 3);
Bmp.SetPixel(x, y, Color.FromArgb(rgb, rgb, rgb));
}
return Bmp;
}

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cms9651

Member

175 Points

573 Posts

Re: Convert an Image to Grayscale - C#

Dec 31, 2012 08:53 AM|LINK

thank you, but I have the same error:
CS0117: 'System.Web.UI.WebControls.Image' does not contain a definition for 'Image'

<asp:Image ID="lblImage2" runat="server" />


    protected void Page_Load(object sender, EventArgs e)
    {

         GrayScale(lblImage2.Image);
    }


    public Bitmap GrayScale(Bitmap Bmp)
    {
        int rgb;
        Color c;

        for (int y = 0; y < Bmp.Height; y++)
            for (int x = 0; x < Bmp.Width; x++)
            {
                c = Bmp.GetPixel(x, y);
                rgb = (int)((c.R + c.G + c.B) / 3);
                Bmp.SetPixel(x, y, Color.FromArgb(rgb, rgb, rgb));
            }
        return Bmp;
    }

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cms9651

Member

175 Points

573 Posts

Re: Convert an Image to Grayscale - C#

Jan 13, 2013 11:30 AM|LINK

Can you help me?
Any suggestions?

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kidshaw

Participant

1158 Points

252 Posts

Re: Convert an Image to Grayscale - C#

Feb 05, 2013 09:10 PM|LINK

Reference system.drawing.imaging instead. That is the library for image manipulation as described. I'm interested to know why your convert to Gray favours the green channel? You should also replicate alpha channel too just in case.

If it helps, mark as answer - your approval helps with my recovery ;)