Playing with Images in ASP.NET

• Download source code - 172 KB

Introduction

Hello friends, in this article we are going to learn two things related to images and file upload control. This article is for complete beginners who are working with File Upload control and images and do not know much about the below mentioned points. I have divided this article into three sections:

1. Finding the height and width of an image.
2. Appending a time stamp with the image name while saving it.
3. Adding a watermark on an image while uploading it.

First, before looking at the code, this is how my sample page looks like...

Explanation

1. Finding the height and width of an image – Sometimes in our applications we allow our users to upload their images. And in some cases we want them to upload an image of a specific dimension. For example – 450x900. Below is the code for finding the height and width.

Code to check the height and width of an image – Default.aspx page code

ASP.NET

<%@ Page Title="Home Page" Language="C#" MasterPageFile="~/Site.master" 
         AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">
</asp:Content>
<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">
    <h2>
        Welcome to ASP.NET!
    </h2>
    <p>
        Please Select an Image file:    
        <asp:FileUpload ID="FUP_WatermarkImage" runat="server" />
    </p>
    <p>
        <asp:Button ID="btnUpload" runat="server" Text="Upload Image" onclick="btnUpload_Click" />
    </p>
    <p>
        <asp:Image ID="imgUploadedImage" runat="server" Width="250" 
               Height="250" BorderColor="Black" BorderStyle="Solid" BorderWidth="1" />
    </p>
</asp:Content>

Note – Please note that in the ASP.NET Image control I have kept the width and height as 250 for both. So in my code I am going to check the images whether its height and width exceeds 250*250 dimension. If it exceeds, then I’ll show an error message to the user and won’t allow him to upload the image.

C#

protected void btnUpload_Click(object sender, EventArgs e)
{
    if (Fupload_WatermarkImage.HasFile)
    {
        string FileType = Path.GetExtension(Fupload_WatermarkImage.PostedFile.FileName).ToLower().Trim();
        // Checking the format of the uploaded file.
        if (FileType != ".jpg" && FileType != ".png" && FileType != ".gif" && FileType != ".bmp")
        {
            string alert = "alert('File Format Not Supported. Only .jpg, .png, .bmp and .gif file formats are allowed.');";
            ScriptManager.RegisterStartupScript(this, GetType(), "JScript", alert, true);
        }
        else
        {
            // Getting the stream of the selected image and assign it to the Image Object.
            System.Drawing.Image UploadedImage = System.Drawing.Image.FromStream(Fupload_WatermarkImage.PostedFile.InputStream);
            // Checking if the Width or height is greater than 250px
            if (UploadedImage.PhysicalDimension.Width > 250 || UploadedImage.PhysicalDimension.Height > 250)
            {
                string alert = "alert('Image size should be exactly 250*250 dimension. Your Current Image width is " + 
                  UploadedImage.PhysicalDimension.Width + " and height is " + 
                  UploadedImage.PhysicalDimension.Height + ".');";
                ScriptManager.RegisterStartupScript(this, GetType(), "JScript", alert, true);
            }
            else
            {
                // SOME CODE COMES HERE...
            }
        }
    }
}

User tries to upload image with a dimension of more than 250 pixels

Image indicating the width of the uploaded image–



Image indicating the height of the uploaded image–



Error message shown to the user



2. Appending a time stamp with the image name while saving it – Sometimes a user might add an image with the same name twice. In that case if you want to differentiate between the images, then you can attach the current timestamp with the image name. Below is the code for doing the same.
C#

// Getting the file name of the selected image
string FileName = Path.GetFileNameWithoutExtension(Fupload_WatermarkImage.PostedFile.FileName);
// Getting the file extension of the selected image
string FileExtension = Path.GetExtension(Fupload_WatermarkImage.PostedFile.FileName);
// Creating a complete relative path for storing the image.
// And also attaching the datetime stamp with the image name.
string path = "Watermarked Images/" + FileName + 
       DateTime.Now.ToString("yyyy-MM-dd HHmmtt") + FileExtension;
                    
// Saving the Image.
Fupload_WatermarkImage.SaveAs(Server.MapPath(path));
                    
// Assigning the uploaded image url to the Image control.
imgUploadedImage.ImageUrl = path;
if (!String.IsNullOrEmpty(imgUploadedImage.ImageUrl))
{
    // Showing a notification of success after uploading.
    string alert = "alert('Image uploaded successfully');";
    ScriptManager.RegisterStartupScript(this, GetType(), "JScript", alert, true);
}

Note – You can easily understand the code since I have added the appropriate comments with each line of my code. The line of code marked in yellow is where I am attaching my current time stamp with the image name. Below is the image which shows how exactly the image is saved.

Selected an image with height and width less than 250 pixels



Code debugged



The current time is attached with the image name. So the next time even if I upload an image with the same name, I can still upload it since the timestamp differentiates it.

Final output – Image being displayed in the Image control



Image uploaded in the folder–



3. Watermarking an image – Sometimes when we add images from our application, we do not want other users to copy it or use it in their applications. Watermarking is the option which helps protect our images from getting copied or used by other users. Below is the code written to add watermark on an image before saving it in a folder.

Code for watermarking – Content marked in yellow actually writes / watermarks the image.

C#

// Create an Image Object and fill it with the stream of the selected image.
System.Drawing.Image image = 
  System.Drawing.Image.FromStream(Fupload_WatermarkImage.PostedFile.InputStream);
                    
// Get the height and width of an image.
int width = image.Width;
int height = image.Height;
// Creating the Bitmap Object and assigning the width and height of the image.
// It internally creates a graphical image with the same dimension.
System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(width, height);
                    
// Creating a Graphics Object from the Bitmap Object.
System.Drawing.Graphics graphics1 = System.Drawing.Graphics.FromImage((System.Drawing.Image)bmp);
                    
// Assigning few properties to the Graphics Object, to maintain the quality of the image.
graphics1.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
graphics1.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
graphics1.Clear(System.Drawing.Color.Transparent);
graphics1.DrawImage(image, 0, 0, width, height);
// Create the Font and the Brush Object and assign appropriate parameters inorder to add watermark to the image.
System.Drawing.Font font = new System.Drawing.Font("Arial", 20);
System.Drawing.SolidBrush brush = new System.Drawing.SolidBrush(System.Drawing.Color.Aqua);
// Drawstring actually writes / watermarks the image with the specified content.
// Parameters contain :- Watermark Content, font style, brush used, x and y position for the string to be written
graphics1.DrawString("C Sharp Corner", font, brush, 25F, 115F); 
                    
// Create the image object from the bitmap and then use it to save the watermarked image in the folder.
System.Drawing.Image newImage = (System.Drawing.Image)bmp;
// Getting the file name of the selected image
string FileName = Path.GetFileNameWithoutExtension(Fupload_WatermarkImage.PostedFile.FileName);
// Getting the file extension of the selected image
string FileExtension = Path.GetExtension(Fupload_WatermarkImage.PostedFile.FileName);
// Creating a complete relative path for storing the image. And also attaching the datetime stamp with the image name.
string path = "Watermarked Images/" + FileName + DateTime.Now.ToString("yyyy-MM-dd HHmmtt") + FileExtension;
// Saving the Watermarked Image in the specified folder
newImage.Save(Server.MapPath(path));
// Assigning the uploaded image url to the Image control.
imgUploadedImage.ImageUrl = path;
// Disposing the Graphics Object and other resources from the memory.
graphics1.Dispose();
if (!String.IsNullOrEmpty(imgUploadedImage.ImageUrl))
{
    // Showing a notification of success after uploading.
    string alert = "alert('Image uploaded successfully');";
    ScriptManager.RegisterStartupScript(this, GetType(), "JScript", alert, true);
}

Note – For understanding the code, I have added the appropriate comments with the code.

Final output of the above code – The watermark appears on the image in Cyan (Blue) color. The text is “C# Corner”.



Image saved in the folder with watermark–

So this was a simple application where we played with images while uploading it to a folder. Hope you liked it and that this article helped you... Don’t forget to leave your comments. It always encourages me to move ahead... :-)

If you want to check the entire code, please find the attached code file with this article.