Batch Convert PNG-8 Images to WebP Preserving Original Indexed Color Palette

Introduction

In this article, we will discuss how to batch convert PNG-8 images to WebP format while preserving the original 8-bit color palette on a Windows 11 operating system. PNG-8 is a popular image format that uses an indexed color palette, which is limited to 256 colors. WebP is a modern image format that provides lossless and lossy compression for images on the web. WebP images are smaller in size compared to PNG images, which helps to improve the page loading time of a website.

Why Preserve the Original Color Palette?

Preserving the original color palette is important when converting PNG-8 images to WebP format because it ensures that the converted images look identical to the original images. The color palette of a PNG-8 image is optimized for that specific image, and any changes to the color palette can result in a loss of image quality.

What is an Indexed Color Palette?

An indexed color palette is a table that contains a set of colors that are used in an image. Each pixel in the image is assigned a index number that corresponds to a color in the palette. The advantage of using an indexed color palette is that it reduces the size of the image file.

Converting PNG-8 Images to WebP Format

To convert PNG-8 images to WebP format while preserving the original indexed color palette, we can use a command-line tool called cwebp. cwebp is a lossless and lossy image converter developed by Google that supports converting images to WebP format.

Installing cwebp on Windows 11

To install cwebp on Windows 11, we can use the Chocolatey package manager. Chocolatey is a package manager for Windows that allows us to install software and tools using the command line.

choco install cwebp

After running the above command, cwebp will be installed on our system.

Converting PNG-8 Images to WebP Format

To convert PNG-8 images to WebP format while preserving the original indexed color palette, we can use the following command:

cwebp -lossless -index_color_table_size=256 input.png -o output.webp

Let's break down the command:

• cwebp: Invokes the cwebp command-line tool.
• -lossless: Ensures that the conversion is lossless, which means that the image quality will not be degraded.
• -index_color_table_size=256: Specifies that the original indexed color palette with 256 colors should be preserved.
• input.png: The name of the PNG-8 image that we want to convert.
• -o output.webp: The name of the output WebP image.

Batch Converting PNG-8 Images to WebP Format

To batch convert PNG-8 images to WebP format while preserving the original indexed color palette, we can use the following PowerShell script:

$inputFolder = "C:\path\to\input\folder"
$outputFolder = "C:\path\to\output\folder"

Get-ChildItem $inputFolder -Filter "*.png" | ForEach-Object {
 $inputFile = $_
 $outputFile = $inputFile.FullName.Replace($inputFolder, $outputFolder).Replace(".png", ".webp")
 cwebp -lossless -index_color_table_size=256 $inputFile -o $outputFile
}

Let's break down the script:

• $inputFolder: The path to the folder that contains the PNG-8 images.
• $outputFolder: The path to the folder where we want to save the output WebP images.
• Get-ChildItem $inputFolder -Filter "*.png": Gets all the PNG-8 images in the input folder.
• $_: Represents the current PNG-8 image.
• $inputFile.FullName.Replace($inputFolder, $outputFolder).Replace(".png", ".webp"): Generates the output file name by replacing the input folder path and file extension with the output folder path and WebP file extension.
• cwebp -lossless -index_color_table_size=256 $inputFile -o $outputFile: Invokes the cwebp command-line tool to convert the PNG-8 image to WebP format while preserving the original indexed color palette.

In this article, we discussed how to batch convert PNG-8 images to WebP format while preserving the original indexed color palette on a Windows 11 operating system. We covered the key concepts, subtitles, and provided a detailed context on the topic. We using cwebp command-line tool to convert the images and provided a PowerShell script to batch convert the PNG-8 images.

References

• cwebp Documentation
• cwebp on Chocolatey
• PowerShell Documentation