jpegtran Command in Linux
jpegtran is a Linux command that allows you to perform lossless transformation on JPEG images. This means that you can modify your images without losing any quality. The jpeg command helps you rotate, flip, and transpose images or convert them to grayscale. The command is pretty useful in case you want to optimize images by reducing their size or improving compression. Apart from that, the command can also help crop images and remove unnecessary padding.
Table of Contents
Here is a comprehensive guide to the options available with the jpegtran command −
- Installation of jpegtran Command
- Syntax of jpegtran Command
- jpegtran Command Options
- Examples of jpegtran Command in Linux
Installation of jpegtran Command
By default, the jpegtran command isnât preinstalled on your Linux systems. However, it can be installed directly from the default systemâs package manager.
1. Ubuntu/Debian
sudo apt install libjpeg-progs
2. CentOS/RHEL
sudo yum install libjpeg-turbo-utils
3: Fedora
sudo dnf install libjpeg-turbo-utils
4: Arch Linux
sudo pacman -S libjpeg-turbo
5: OpenSUSE
sudo zypper install libjpeg8
Syntax of jpegtran Command
The general syntax for jpegtran on Linux is as follows −
jpegtran [switches/options] [inputfile]
Where −
- [switches/options] are the various options you can use to specify the type of transformation you want to perform on the JPEG file.
- [inputfile] is the path to the input JPEG file that you want to transform.
jpegtran Command Options
The following are some options or switches that can be used with the jpegtran command in Linux −
| Option | Description |
|---|---|
| -arithmetic | Uses arithmetic coding instead of Huffman coding for potentially smaller files. |
| -flip horizontal | Mirrors the image horizontally (left to right). |
| -flip vertical | Mirrors the image vertically (top to bottom). |
| -grayscale | Turns the image to black and white, removing all colors. |
| -optimize | Optimizes the entropy encoding parameters to reduce file size without quality loss. |
| -outfile | Specifies the output fileâs name. |
| -progressive | Creates a progressive JPEG, which loads in stages for better viewing on slow connections. |
| -restart N | Adds a restart marker after every N MCU rows or blocks to enhance error recovery. |
| -rotate 180 | Rotates the image 180 degrees. |
| -rotate 270 | Rotates the image 270 degrees clockwise (or 90 degrees counterclockwise). |
| -rotate 90 | Rotates the image 90 degrees clockwise. |
| -scans file | Uses a custom scan script from a specified file to control encoding order. |
| -transpose | Flips the image along its diagonal from the top-left to the bottom-right corner. |
Examples of jpegtran Command in Linux
Letâs explore a few examples of jpegtran command in Linux −
1. Horizontal Flip
If you want to create a mirror image of your photo along the vertical axis, you can use the -flip horizontal option with jpegtran. This command will take your original image and produce a new one that is flipped horizontally. For example −
jpegtran -flip horizontal path/to/image.jpg > path/to/output.jpg
2. 90-degree Rotation
To rotate an image by 90 degrees clockwise, you can use the -rotate 90 option. This is handy when you need to change the orientation of a photo, such as when a picture is taken in landscape mode but you want it in portrait mode. For example −
jpegtran -rotate 90 path/to/image.jpg > path/to/output.jpg
This command will rotate the image and save the result in a new file.
3. Grayscale Conversion
If you need to convert a color image to grayscale, the -grayscale option will remove all color information, leaving you with a black-and-white image. This can be useful for artistic purposes or to reduce file size. For example −
jpegtran -grayscale path/to/image.jpg > path/to/output.jpg
The resulting image will only contain shades of gray, which can highlight textures and contrasts.
4. Image Cropping
To crop an image to a specific rectangular region, use the -crop WxH+X+Y option. Here, W denotes the width, H is the height, while X and Y are the coordinates of the top-left corner of the cropping area. Hereâs an example −
jpegtran -crop 100x100+10+10 path/to/image.jpg > path/to/output.jpg
This command will extract a 100x100 pixel area starting 10 pixels from the left and 10 pixels from the top of the original image.
5. Diagonal Transpose
For a diagonal flip along the upper-left to lower-right axis, the -transpose option is used. This can create interesting effects by flipping the image diagonally. For example −
jpegtran -transpose path/to/image.jpg > path/to/output.jpg
This command mirrors the image along the diagonal axis, which can be useful for certain types of image corrections or artistic transformations.
6. Diagonal Transverse
To flip an image diagonally along the upper-right to lower-left axis, you can use the -transverse option. This is another way to create a diagonal mirror effect. Hereâs an example −
jpegtran -transverse path/to/image.jpg > path/to/output.jpg
This command will produce a new image that is mirrored diagonally in the opposite direction compared to the -transpose option.
Conclusion
The jpegtran is a powerful tool for performing lossless transformations on JPEG files. It offers a range of functionalities such as mirroring, rotating, transposing, and converting images to grayscale, all while maintaining the original image quality.
In this tutorial, we have provided details on the basic syntax, options, and practical examples of the command. Whether you need to flip an image, correct its orientation, or convert it to grayscale, jpegtran is a straightforward and efficient way to handle such tasks.