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Reducing JPEG Picture Quality using C#Learn how to create an application that reduces the quality of JPEG pictures from a folder and then puts the new pictures into another folder. |
On Sunday, October 7th 2007 at 01:30 AM By Andrew Pociu (View Profile)   (Rated 4.5 with 15 votes) |
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 Download this project (Visual Studio 2005)
Changing the picture quality of a JPEG fileIn this C# programming tutorial we're going to create a quite useful little application - one that takes every JPEG picture in a folder and changes its quality to a desired rate, which obviously reduces the size of the JPEG file. Thus, aside from using an encoder to reduce the quality of the picture, you'll also learn how to scan a folder for files of a certain type, and put them in a ListBox.Designing the applicationFire up Visual Studio 2005 and start a new C# Windows Application. On it draw two buttons - btnOpen and btnReduce - they will be used to select the folder where you want to look for the pictures to be modified, and the folder where the modified pictures will be stored. The big control on this page is the ListBox control named lstPhotos, it is where the list of files to be reduced in quality will be stored. Then there's numQual - a NumericUpDown with values of 1 to 100 - which will define the quality to which we want the pictures reduced. Finally the last control to add to the form is prgReduce - a ProgressBar that keeps track of the progress made in resizing all the files. You will see that the progress bar works quite fine, even though we're not going to use a separate thread for the picture reducing code. Remember when I said we added our last component to the form? I lied. We still need the two dialogs that fire up when the btnOpen and btnReduce are clicked. They allow the user to select the folder where they want the files to be picked up from, and where the new ones are to be dropped. These two are FolderBrowserDialogs and are named as follows:  The code behind the applicationSince we're going to be working with graphic files and directories, the following two using statements are appropriate:using System.IO; using System.Drawing.Imaging; Our code is divided into two: the scanning of the folder from where we pick up the pictures, and the quality reducing and file saving code. The first part happens inside the click event of btnOpen: private void btnOpen_Click(object sender, EventArgs e) { if (fbdOpen.ShowDialog() == DialogResult.OK) { // Clear any previous items in the list lstPhotos.Items.Clear(); // Run a loop through all the files in the directory at the selected path foreach(string Filename in Directory.GetFiles(fbdOpen.SelectedPath)) { // We'll create a new FileInfo object from the file path FileInfo fiPicture = new FileInfo(Filename); // If it's a JPEG file if (fiPicture.Extension.ToLower() == ".jpeg" || fiPicture.Extension.ToLower() == ".jpg") { // Add it to the list of files lstPhotos.Items.Add(Filename); } } } // We want the ProgressBar to have the same maximum value as the number of pictures to resize prgReduce.Maximum = lstPhotos.Items.Count; } Being commented, the code should be pretty easy to figure out. All we do is loop through the files in the directory and if they have the jpeg/jpg extension, we add them to the list. So let's move on to the click event of btnReduce, where the second and final piece of code exists, which is more interesting since its the actual code that reduces the quality: private void btnReduce_Click(object sender, EventArgs e) { // Reset the progress bar prgReduce.Value = 0; // Show the FolderBrowserDialog where the user selects where to save the files if (fbdSave.ShowDialog() == DialogResult.OK) { // We will store the correct image codec in this object ImageCodecInfo iciJpegCodec = null; // This will specify the image quality to the encoder EncoderParameter epQuality = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (int)numQual.Value); // Get all image codecs that are available ImageCodecInfo[] iciCodecs = ImageCodecInfo.GetImageEncoders(); // Store the quality parameter in the list of encoder parameters EncoderParameters epParameters = new EncoderParameters(1); epParameters.Param[0] = epQuality;
// Loop through all the image codecs for (int i = 0; i < iciCodecs.Length; i++) { // Until the one that we are interested in is found, which is image/jpeg if (iciCodecs[i].MimeType == "image/jpeg") { iciJpegCodec = iciCodecs[i]; break; } }
// Loop through the files in the list foreach (string strFile in lstPhotos.Items) { // Take another step on the progress bar prgReduce.PerformStep();
// Create a new Image object from the current file Image newImage = Image.FromFile(strFile);
// Get the file information again, this time we want to find out the extension FileInfo fiPicture = new FileInfo(strFile); // Save the new file at the selected path with the specified encoder parameters, and reuse the same file name newImage.Save(fbdSave.SelectedPath + "\\" + fiPicture.Name, iciJpegCodec, epParameters); } } // Open the folder containing the new items System.Diagnostics.Process.Start(fbdSave.SelectedPath.ToString()); } What this code does is to retrieve the correct image codec for JPEG files; we will need it in order to change the quality of the file. The code can be improved nicely if put into its separate class and into its separate thread. It would also help the progress bar act more smoothly. Compile the application and run. You just built yourself a little JPEG processing application:  |
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Current Comments
Very good!
This helps a lot if you have much photos and want to upload them!
I will _NEVER_ again use MS Paint to edit each separate photo ^^
excellant
Very nice
Great stuff! Thanks!
thank you very much
Hi !
Excellent application. One thing-
do add
newImage.Dispose();
right after this line -
newImage.Save(fbdSave.SelectedPath "\\" fiPicture.Name, iciJpegCodec, epParameters);
Otherwise, the application becomes a resource hog as all opened images remain in memory
Thank you for this. Very useful!
One thing though: I kept on getting a parameter error with the Image Save method. I did a bit of research on the MSDN site and they showed the parameter cast as a Long integer. Once I did that then all worked fine.
The image's colordepth is 8b,but to use your software, the colordepth is becoming 24b,why?
Very useful!!!
Excellent work, it help alot
Thanks
Thx for the post..
Hi,
Can u tel me how to convert .CMP file in to the .jpg or .png or any other image format file...
Thanks in advance........
Thx you for this Veryyyyyyyyy useful..
Thx you for this Veryyyyyyyyy useful..
Good article. Thanks for help.
Whether the quality gets increased or only the size increases... plz rply..
Whether the quality gets increased or only the size increases... plz rply..
hi,its working but the minimum quality can be set is 1, i need to reduce the quality to very very low (i.e -100) inorder to use in a application. tell me how to do this, thanks in advance
hi
how to get jpeg quality of a image?
can get it?
thanks
hi
how to get jpeg quality of a image?
can get it?
thanks
This is a great trick and I didn’t know you can use C# to obtain the info of your computer
This is a great trick and I didn’t know you can use C# to obtain the info of your computer
Does this trick work for Mac too?
Does this trick work for Mac too?
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I have to express my thanks to the writer just for rescuing me from such a difficulty. Because of browsing through the online world and seeing views which were not helpful, I believed my life was done. Existing without the presence of solutions to the problems you've fixed as a result of your main write-up is a crucial case, and the kind which could have in a wrong way affected my entire career if I hadn't discovered your website.
Hello. magnificent job. I did not anticipate this. This is a great story. Thanks!
Once you have recreated the problem and captured these steps, you can save them to a file and send it to your support person, who can then open it up and view
Thank you, thank you :). Great job.
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