How to Use the Command 'guetzli' (with examples)
Guetzli is a command-line utility developed by Google with the primary purpose of compressing JPEG images. This tool optimizes JPEG files by reducing their file size while preserving visual quality as much as possible. It provides options to convert images from PNG format to compressed JPEG and allows users to specify the level of visual quality they desire. Guetzli is particularly valuable for web developers, photographers, and anyone looking to optimize image storage or web page load times.
Use case 1: Compress a JPEG Image
Code:
guetzli input.jpg output.jpg
Motivation:
JPEG images dominate the web due to their capability to store complex graphics with a relatively balanced file size and quality. However, managing the balance between these two can become essential, especially when server storage is limited or when faster web page loading times are desired. Using Guetzli to compress JPEG images allows users to efficiently reduce file sizes while maintaining image quality. This is crucial for optimizing bandwidth usage and improving user experience on websites.
Explanation:
guetzli: The command to run the Guetzli JPEG compression tool.input.jpg: This represents the path and file name of the original JPEG image that needs to be compressed. This is the source image you want to optimize.output.jpg: This is the path and name where the compressed image will be saved. It should be different from the input to avoid overwriting the original file.
Example Output:
Upon successful compression, the output.jpg file will be a smaller and optimized version of input.jpg. Depending on the original and desired output sizes, users could notice a reduction ranging from 20% to 40% without substantial loss in visual quality.
Use case 2: Create a Compressed JPEG from a PNG
Code:
guetzli input.png output.jpg
Motivation:
PNG files, known for lossless quality, can be quite large, which isn’t ideal for web use where serving quick-loading pages is key. Transforming a PNG into a JPEG and compressing it with Guetzli can greatly reduce the size while maintaining an acceptable quality level for most applications. This is particularly beneficial for reducing storage costs and optimizing image-heavy web pages.
Explanation:
guetzli: Executes the Guetzli tool for image compression.input.png: The path and name of the PNG image that you want to convert to JPEG format and compress. Typically, this is used when you want a smaller file size than PNG can provide.output.jpg: The file name and path where the resulting compressed JPEG will be saved. This highlights the use of Guetzli to not only compress but also convert image formats.
Example Output:
A converted and compressed JPEG file, output.jpg, emerges from the original input.png. The resulting JPEG will be significantly smaller, often suitable for sharing online, embedding in websites, or any other uses where smaller file sizes dictate.
Use case 3: Compress a JPEG with Desired Visual Quality
Code:
guetzli --quality 95 input.jpg output.jpg
Motivation:
Not every compression requirement is the same – sometimes, the image quality is paramount even at the expense of smaller file size. With Guetzli’s quality setting, users can specify how much visual quality should be preserved during the compression. This option is especially useful for professional photographers and graphic designers who need high-quality images but still want to benefit from reduced file sizes for distribution or storage.
Explanation:
guetzli: Starts the Guetzli compression utility.--quality 95: This sets the quality of the resulting JPEG. The number is an integer between 84 (lower quality, higher compression) and 100 (highest quality, least compression). Setting it at 95 generally results in high quality with a reasonable file size.input.jpg: The source JPEG that you want to compress.output.jpg: The filename for the compressed image. By selecting a descriptive name, users prevent possibly overwriting the original.
Example Output:
The image output.jpg will be compressed with the quality setting specified. Users will notice that the visual quality of the image remains very similar to the original while benefitting from some degree of file size reduction, depending on the initial image characteristics and desired quality.
Conclusion:
Guetzli provides a powerful and flexible tool for compressing JPEG images, converting PNGs to JPEGs, and setting desired image quality levels. By adjusting these parameters, users can optimize their digital assets for various uses, from enhancing website performance to managing storage effectively without sacrificing meaningful image quality.
