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Posted 25 May 2011

Change Opacity of Image in C#

, 27 May 2011 CPOL
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A tip which enables you to change Opacity of Image in C#
This is a simple tip/trick which enables you to change Opacity of Image using C# by using System.Drawing and System.Drawing.Imaging NameSpaces.
Take a look at how ChangeOpacity(Image img, float opacityvalue) method will enable you to change opacity of Image.
In this given code, System.Drawing Namespace is used to access Bitmap and Graphics classes whereas System.Drawing.Imaging Namespaces is used to access ColorMatrix and ImageAttributes.
ChangeOpacity method has two parameters including img for Image on which opacity will apply, and opacityvalue for set opacity level of form.

using System;
using System.Drawing;
using System.Drawing.Imaging;

namespace ImageUtils
    class ImageTransparency
        public static Bitmap ChangeOpacity(Image img, float opacityvalue)
            Bitmap bmp = new Bitmap(img.Width,img.Height); // Determining Width and Height of Source Image
            Graphics graphics = Graphics.FromImage(bmp);
            ColorMatrix colormatrix = new ColorMatrix();
            colormatrix.Matrix33 = opacityvalue;
            ImageAttributes imgAttribute = new ImageAttributes();
            imgAttribute.SetColorMatrix(colormatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
            graphics.DrawImage(img, new Rectangle(0, 0, bmp.Width, bmp.Height), 0, 0, img.Width, img.Height, GraphicsUnit.Pixel, imgAttribute);
            graphics.Dispose();   // Releasing all resource used by graphics 
            return bmp;

When you will use this method in your program to change opacity of an image in pictureBox control, you need to write code as given below:

float opacityvalue = float.Parse(txtopacityvalue.Text) / 100;
pictureBox1.Image = ImageUtils.ImageTransparency.ChangeOpacity(Image.FromFile("filename"),opacityvalue);  //calling ChangeOpacity Function 

To learn how to use the given code in your program:
Click here[^] to download source code.

[Edited-"Adding Reference Link"]
Reference Article: There-Image Opacity Using C#[^]


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Ravi Ranjan Kr
Software Developer
India India
Microsoft Student Partner | CS Student | MCTS | CP MVP | Crazy Learner | Dreamer

An Indian, who loves his country, believes in freedom, He is an enthusiast Techie and crazy learner. He is passionate about Technologies and social media. He holds bachelor degree of CS in Information Technology and now pursuing Master degree in Computer Application.

He always excited and keen Interested in learning and sharing knowledge. He loves to write blog, learn new things, listen music, taking arts and Playing Games..

He keep himself on the desk of his imagination, hanging around with some inceptions.

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Comments and Discussions

GeneralInteresting solution! Typically I tend to use CCS/jQuery cli... Pin
DrABELL27-May-11 16:02
memberDrABELL27-May-11 16:02 
GeneralRe: Thank you DrABELL :) Pin
RaviRanjankr27-May-11 19:59
mvpRaviRanjankr27-May-11 19:59 

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