how to watermark image with logo in asp.net

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Hi everyone,

I am trying to watermark my image with a logo and for that I am using this function, but I get an image which is not watermarked.

I have not got any error msg, it is poulating data properly but the image which I am getting as output doesn't have the watermarked logo on it.

Here the code which I have posted, it is one which I got from the internet.
I don't understand actually where to use original image and logo, or how to use drawimage to draw logo on the image.

 public Bitmap AddWatermark(Bitmap bImg, Bitmap logo)
{
    Bitmap imgPhoto = bImg;
    int phWidth = imgPhoto.Width;
    int phHeight = imgPhoto.Height;
    Bitmap bmPhoto = new Bitmap(phWidth, phHeight, PixelFormat.Format24bppRgb);
   bmPhoto.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);
   Graphics grPhoto = Graphics.FromImage(bmPhoto);
   System.Drawing.Image imgWatermark = logo;
    int wmWidth = imgWatermark.Width;
    int wmHeight = imgWatermark.Height;
   Bitmap bmWatermark = new Bitmap(bmPhoto);
    bmWatermark.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);
    Graphics grWatermark = Graphics.FromImage(bmWatermark);
    ImageAttributes imageAttributes = new ImageAttributes();
    ColorMap colorMap = new ColorMap();
    colorMap.OldColor = Color.FromArgb(255, 0, 255, 0);
    colorMap.NewColor = Color.FromArgb(0, 0, 0, 0);
    ColorMap[] remapTable = { colorMap };
    imageAttributes.SetRemapTable(remapTable, ColorAdjustType.Bitmap);
    float[][] colorMatrixElements = {
                                            new float[] {1.0f,  0.0f,  0.0f,  0.0f, 0.0f},
                                            new float[] {0.0f,  1.0f,  0.0f,  0.0f, 0.0f},
                                            new float[] {0.0f,  0.0f,  1.0f,  0.0f, 0.0f},
                                            new float[] {0.0f,  0.0f,  0.0f,  1.0f, 0.0f},
                                            new float[] {0.0f,  0.0f,  0.0f,  0.0f, 1.0f}};
    ColorMatrix wmColorMatrix = new ColorMatrix(colorMatrixElements);
    imageAttributes.SetColorMatrix(wmColorMatrix, ColorMatrixFlag.Default,ColorAdjustType.Bitmap);
    int xPosOfWm = ((phWidth - wmWidth) - 10);
    int yPosOfWm = 10;

    grWatermark.DrawImage(imgWatermark,new Rectangle(xPosOfWm, yPosOfWm, wmWidth, wmHeight), 0, 0,wmWidth,wmHeight,GraphicsUnit.Pixel,imageAttributes);   //ImageAttributes Object

    imgPhoto = bmWatermark;
    return imgPhoto;
}

Posted 23-Mar-11 4:55am

RKT S

Updated 23-Mar-11 6:24am

Dalek Dave

v4

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Comments

J a a n s 23-Mar-11 11:48am

Your code is not at all using the original image 'bImg'. Also it is creating a lot of unwanted variables. Please get code from some better source and use it.

Dalek Dave 23-Mar-11 12:25pm

Edited for Grammar, Syntax and Readability.

2 solutions

Solution 2

Refer these articles to understand how it can be done:
Watermark Website Images At Runtime[^]
Dynamic Watermarking Images in C#.NET[^]
Dynamic Watermarking Images in C#.NET-2[^]

Posted 23-Mar-11 5:35am

Sandeep Mewara

Comments

Sergey Alexandrovich Kryukov 23-Mar-11 20:27pm

My 5,
--SA

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Manfred Rudolf Bihy · Accepted Answer · 2011-03-23T05:21:00

Solution 1

The error lies in your color matrix element at position 3,3 (zero based) has to be the opacity. 1.0 means it is totally opaque so you'll see the water mark image over the other image. Try with your color matrix like this:

C#

float[][] colorMatrixElements = {
    new float[] {1.0f,  0.0f,  0.0f,  0.0f, 0.0f},
    new float[] {0.0f,  1.0f,  0.0f,  0.0f, 0.0f},
    new float[] {0.0f,  0.0f,  1.0f,  0.0f, 0.0f},
    new float[] {0.0f,  0.0f,  0.0f,  0.25f,0.0f},
    new float[] {0.0f,  0.0f,  0.0f,  0.0f, 1.0f}};

Matrix element 3,3 is now set to 25 percent opacity so some of the image that is being watermarked will show through.

Hope this helps you!

Look also at this article: Creating a Watermarked Photograph with GDI+ for .NET[^].

Happy coding!

Posted 23-Mar-11 5:21am

Manfred Rudolf Bihy

Comments

Sandeep Mewara 23-Mar-11 11:35am

My 5! Found the mistake too along with helpful link.

Dalek Dave 23-Mar-11 12:25pm

Good Catch and Answer.

Sergey Alexandrovich Kryukov 23-Mar-11 20:26pm

Very good, my 5.
--SA

RKT S 23-Mar-11 21:43pm

thnaks manfred...

RKT S 24-Mar-11 0:09am

hi manfred....i did the changes which you asked me to do... but still the watermark image is the one without logo on it... plz help and let me know if i am doing something wrong here.. the final function which i have used is

public Bitmap AddWatermark(Bitmap bImg, Bitmap logo)
{

Bitmap bmPhoto = bImg;
//bmPhoto.SetResolution(bImg.HorizontalResolution,bImg.VerticalResolution);
Graphics grPhoto = Graphics.FromImage(bmPhoto);

Bitmap imgWatermark=logo;
int wmWidth = imgWatermark.Width;
int wmHeight = imgWatermark.Height;

//Create a Bitmap based on the previously modified photograph Bitmap
ImageAttributes imageAttributes = new ImageAttributes();
ColorMap colorMap = new ColorMap();
colorMap.OldColor = Color.FromArgb(255, 0, 255, 0);
colorMap.NewColor = Color.FromArgb(0, 0, 0, 0);
ColorMap[] remapTable = { colorMap };
imageAttributes.SetRemapTable(remapTable, ColorAdjustType.Bitmap);
float[][] colorMatrixElements = {
new float[] {1.0f, 0.0f, 0.0f, 0.0f, 0.0f},
new float[] {0.0f, 1.0f, 0.0f, 0.0f, 0.0f},
new float[] {0.0f, 0.0f, 1.0f, 0.0f, 0.0f},
new float[] {0.0f, 0.0f, 0.0f, 0.3f, 0.0f},
new float[] {0.0f, 0.0f, 0.0f, 0.0f, 1.0f}};
ColorMatrix wmColorMatrix = new ColorMatrix(colorMatrixElements);
imageAttributes.SetColorMatrix(wmColorMatrix, ColorMatrixFlag.Default,ColorAdjustType.Bitmap);
grPhoto.DrawImage(imgWatermark, new Rectangle(0, 0, wmWidth, wmHeight), 0, 0, wmWidth, wmHeight, GraphicsUnit.Pixel, imageAttributes);

return bmPhoto;

}

Manfred Rudolf Bihy 24-Mar-11 2:30am

Have you tried the source code from the CP article I gave in my post? It looks like it's exactly what you're trying to achieve. Please have a go at that.

rkttttt 24-Mar-11 3:04am

yeah manfred....i have got my code from there only...studied it properly and then made necessary changes in the code...but still logo pasted on image is not visible....however i get a new image but without any logo....i dont understand the mistake....plz help...

RKT S 26-Mar-11 0:24am

thanks manfred...it worked...i got the mistake...

Manfred Rudolf Bihy 27-Mar-11 20:02pm

Sorry for not replying sooner, but I'm sure glad you could work it out!