How to use XnConvert to batch change the brightness, saturation, contrast, file format, etc. of multiple images

Free software called XnConvert allows you to change the brightness, saturation, contrast, etc. of multiple images at once. You can also edit metadata, rotate, crop, resize, blur, emboss, sharpen, and change the file format. It supports over 500 input and 70 output formats , including JPEG, TIFF, PNG, GIF, WebP, PSD, JPEG2000, JPEG-XL, OpenEXR, camera RAW, AVIF, HEIC, HEIF, PDF, DNG, DDS(Direct Draw Surface) and CR2. You can also use CLI (Command Line Interface) with NConvert .
In addition, this site also introduces how to batch convert images using the GIMP plugin BIMP . Please take a look at this as well.

Use the GIMP plugin BIMP to change brightness, contrast, etc. of multiple images at once

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Installing XnConvert

Open the official XnConvert website of XnSoft. Then scroll down this screen.

XnConvert official website

A download button will then appear. Click the button for your desired OS. For Windows, simply select "Setup Win 64bit."
This will download an installer called "XnConvert-win-x64.exe." This file is approximately 25MB in size and will take just a few seconds to download.

Double-click the installer to begin the installation. Initially, a User Account Control screen like this will appear. Click "Yes".

Next, select the language you want to use for the installation.

Next is the End User License Agreement acceptance screen. Select "I accept the agreement".

Next, you will need to select the installation folder. There is no need to change this.

Next is registration to the start menu. There is no need to change anything.

Next you can choose to create a desktop shortcut and a quick launch shortcut. Choose either option according to your preference.

Finally, you will see the installation conditions confirmation screen. Click the [Install] button.

The installation will then begin. It will take about a dozen seconds.

When you see this screen, the installation is complete.

How to use XnConvert

As an example, we will change the brightness, saturation, and contrast of multiple images at once.

The first time you start the app, you'll see a screen like this. You can choose the display language, theme, where to store configuration files, and how often to check for software updates. There shouldn't be any need to change anything. Set it to your liking.
These settings can be changed on the [Settings] screen.
By default, the XnConvert configuration file is saved in "C:\Users\[username]\AppData\Roaming\XnConvert".

Setting the Input
This is the XnConvert startup screen. Click on the tabs at the top to set up the conversion process.
First, there is the [Input] screen. Press the [Add Files] or [Add Folder] button in the top left of the screen to specify the input file/folder to be converted.

Setting the Actions
Next, specify the action to be taken for the conversion. When you click the [Actions] tab, you'll see a screen like this. A preview is displayed on the right half of the screen.
Click the [Add Action] button in the top left of the screen.
If you just want to convert the file format, there is no need to specify an action. Proceed to setting up the output.

Select [Adjust] - [HLS(Hue/Luminance/Saturation)].

This will add an "Action" to the left of the screen. You can change the hue/brightness/saturation by manipulating each slider. The image on the right of the screen will preview the results of your settings. Clicking the orange (Return) icon at the right end of the slider will reset the slider to its default value.
Each time you click the (Enabled) checkbox in the top right of the "Action" screen, you can turn this "Action" on/off. The preview image will change.
You can delete this "Action" by clicking the red (Minus) icon in the top right of the "Action" screen.

Next, add an "action" to adjust the contrast. Select [Adjust] - [Adjust].

This will add a new "Action" to the left of the screen. Operating each slider will allow you to change the brightness/contrast/gamma values.
You can change the order of the "Actions" by clicking the green (Up) or (Down) icon in the upper right of the "Actions" screen. The results change depending on the order of the "Actions". Think about the appropriate order.

Setting the Output
Finally, specify the output destination for the conversion results. When you click the [Output] tab, you will see a screen like this.
In the "Output" field, you can choose whether to save the converted result in the same folder as the input or in a different folder.
In the "File name" field, you can specify how to name the converted file. If you specify "{Filename}", the converted file will be saved with the same name as the original file. Click the icon on the far right of this field to select various naming methods.
You can specify the output file format in the "Format" field. Set this if you want to convert to a format different from the original file format.
There are many other options. Set it to your liking.
Once you've finished the settings, click the (Convert) button at the bottom right of the screen to begin batch conversion.
You can also save the settings as a preset to a file or restore them from a file in the "Preset" column at the bottom left of the screen.

While conversion is in progress, the screen will switch to the [Status] tab. The conversion is complete when the "Total time" appears in the bottom left of the screen. The conversion results should be saved in the specified output folder.