What is the WEBP image format? What are the differences between PNG, JPG, WEBP and GIF?
PNG, JPG, WebP, and GIF are the three most commonly used image formats on the market. Before discussing their differences, let me briefly introduce the basics of images.
An image is composed of many pixels, each of which can only store one color. If an image format is 8-bit, it means each pixel can represent 2^8 (256) colors. The higher the bit depth of an image format, the more colors a pixel can represent, resulting in richer images.
Alpha transparency channel: An 8-bit grayscale channel that uses 256 levels of gray to record transparency information in an image, defining transparent, opaque, and semi-transparent areas. Black indicates transparency, white indicates opacity, and gray indicates semi-transparency.
Next, I will explain PNG, JPG, WebP, and GIF images in terms of bit depth, transparency support, lossy or lossless compression, and support for animated images.
PNG
PNG comes in three formats: PNG8, PNG24, and PNG32. PNG8 means each pixel is 8-bit. PNG24 means each pixel is 24-bit. PNG32 means each pixel is 32-bit. Thus, PNG32 can represent more colors than PNG8.
PNG supports transparency.
PNG8 has a 1-bit Boolean transparency channel (either fully transparent or fully opaque). PNG24 uses the Alpha transparency channel, which is an 8-bit (256-level) Boolean transparency channel (semi-transparency), offering 16 million colors.
PNG uses lossless compression. Android uses PNG format images to ensure compatibility across different phones. If JPG were used, images might appear blurry on high-resolution phones.
Although PNG is lossless, some websites like TinyPNG can perform lossy compression on PNG images. As explained on TinyPNG's official website:
When you upload a PNG (Portable Network Graphics) file, similar colors in your image are combined. This technique is called “quantization”. By reducing the number of colors, 24-bit PNG files can be converted to much smaller 8-bit indexed color images. All unnecessary metadata is stripped too. The result: better PNG files with 100% support for transparency.
The principle is to represent similar 24-bit pixels with 8-bit and remove unnecessary metadata. This is lossy compression, but the difference is barely noticeable to the naked eye.
PNG does not support animated images.
JPG
JPG, also known as JPEG, uses the exact same compression algorithm. The two names exist because older Windows systems only supported file extensions with three characters, so JPEG was shortened to JPG for compatibility. Modern Windows systems now support longer extensions, but the JPG name has persisted due to historical reasons.
JPG is 24-bit.
JPG does not support transparency.
JPG uses lossy compression. Each save results in data loss, so avoid saving repeatedly to prevent image degradation.
JPG does not support animated images.
WebP
WebP is an image format invented by Google. WebP images are smaller in size while maintaining the same visual quality.
Initially, WebP did not support transparency, but Google later added this feature.
WebP offers both lossless and lossy compression with high compression ratios.
WebP supports animated images.
GIF
GIF is 8-bit.
GIF supports transparency.
GIF uses lossy compression. Repeatedly saving GIFs will gradually degrade image quality.
GIF can store multiple layers, making it suitable for animated images.