iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
PNG compression itself never discards image data. Reducing the number of colors in a PNG is a separate step, and that step can change pixel values. The file format is lossless; a palette reduction is a quantization decision that you make before or during encoding.
Why the two claims don’t conflict
The PNG format, defined in the W3C Portable Network Graphics (PNG) Specification (Third Edition), compresses image data with a lossless method. Whatever pixel values go into the encoder come back out unchanged when the file is decoded. That guarantee covers the compression stage only.
Palette reduction happens earlier. When an image with many colors is mapped to a smaller set of colors, some original pixels must take a different color. Once that mapping is done, the lossless compressor faithfully preserves the reduced image, including its changes. So a PNG can be lossless in the file-format sense and still look different from the photograph it started as.
What an indexed-color PNG actually stores
PNG supports several color types: grayscale, truecolor (red, green, and blue samples), grayscale with alpha, truecolor with alpha, and indexed color. Indexed color is the type that uses a palette.
#1 Best Overall
- AI Photo Editor Software For Fast Editing: AI editor with auto enhancements, portrait retouching, sky replacement, and lighting tools. Improve photos in seconds with fast, high-quality results.
- Advanced Editing Tools & Creative Effects: AI tools for object removal, relighting, background edits, color grading, and effects. Enhance details and create pro images with minimal effort.
- Standalone App Or Lightroom Plugin: Use as a standalone editor or plugin for Adobe Lightroom and Photoshop. Easily fits into your workflow for flexible, efficient editing.
- Supports RAW, JPEG, PNG & Multiple Platforms: Works with all most common formats. Compatible with Windows and macOS. Ideal for photographers, designers, creators, and beginners.
- Digital License Key: Includes Luminar license key for Windows, MacOS, Mobile (IOS & Android) and Web. Lifetime access to the apps.
In an indexed-color PNG, each pixel stores an index that points to an entry in a palette. The palette entries hold the actual colors, and each entry uses 8-bit samples. The bit depth recorded for the image counts the bits in each index, not the precision of the colors in the palette. The specification permits index depths of 1, 2, 4, or 8 bits, which sets a hard ceiling on how many palette entries an image can address:
| Index bit depth | Maximum palette entries addressable | Typical use |
|---|---|---|
| 1 bit | 2 | Simple two-tone artwork, line drawings |
| 2 bits | 4 | Very limited color sets |
| 4 bits | 16 | Small icons, simple graphics |
| 8 bits | 256 | Most palette-based images |
The maximum counts follow directly from the index size: 2 to the power of the bit depth. An image that needs more distinct colors than its index depth allows cannot be stored as indexed color without reduction.
Rank #2
![WavePad Audio Editing Software - Professional Audio and Music Editor for Anyone [Download]](https://m.media-amazon.com/images/I/B1fcLEGCs6S.png._SL160_.png)
- Full-featured professional audio and music editor that lets you record and edit music, voice and other audio recordings
- Add effects like echo, amplification, noise reduction, normalize, equalizer, envelope, reverb, echo, reverse and more
- Supports all popular audio formats including, wav, mp3, vox, gsm, wma, real audio, au, aif, flac, ogg and more
- Sound editing functions include cut, copy, paste, delete, insert, silence, auto-trim and more
- Integrated VST plugin support gives professionals access to thousands of additional tools and effects
When a palette conversion is exact
Conversion to an indexed image is lossless only when every color the source uses fits into the palette. If an image has 200 distinct colors and you encode it with an 8-bit index, all 200 can be stored exactly. The output is then pixel-for-pixel identical to the source.
Recommended Free Tools
The test is therefore a count of distinct colors, not the appearance of the image. A flat logo, a chart with a fixed color scheme, or a screenshot of a limited interface often meets the condition. A photograph usually does not. Once the distinct-color count exceeds the palette capacity, at least some pixels must change.
Rank #3
- GIMP – The #1 alternative and fully compatible with Adobe Photoshop and Adobe Photoshop Elements files, it is the ultimate fully featured digital image and photo editing software. Restore old photos, change the background, enhance and manipulate images, or simply create your masterpiece from scratch. Multilingual - English, Spanish (Español) and more languages supported.
- Full Tool Suite - Graphic designers, photographers, illustrators, artists and beginners can utilize many tools including channels, layers, filters, effects and more. A plethora of file formats are supported including .psd, .jpg, .gif, .png, .pdf, .hdr, .tif, .bmp and many more.
- Full program that never expires - Free for-life updates and a lifetime license. No yearly subscription or key code is required ever again!
- Multi-Platform Edition DVD-ROM Disc – Compatible with Microsoft Windows PC and Mac.
- PixelClassics Bonus Content – Access to 2.7 MILLION royalty-free stock images photo repository, Installation Menu (PC only), Quick Start Guides and comprehensive User Manual PDF.
What quantization changes
When the palette is too small, an encoder chooses a set of representative colors and maps each source pixel to the nearest one. The choice of representatives and the mapping rule both affect the result, and they vary between tools. Two encoders given the same settings can produce different palettes.
The visible effect depends on the image. Smooth gradients, such as skies, skin tones, and soft shadows, are the most likely to show banding, where a continuous change turns into visible steps between flat bands of color. Detailed photographs may lose subtle tones without an obvious pattern. Flat graphics with few colors typically change little if the palette covers their colors.
Rank #4
- GIMP – The #1 alternative and fully compatible with Adobe Photoshop and Adobe Photoshop Elements files, it is the ultimate fully featured digital image and photo editing software. Restore old photos, change the background, enhance and manipulate images, or simply create your masterpiece from scratch. Multilingual - English, Spanish (Español) and more languages supported.
- Full Tool Suite - Graphic designers, photographers, illustrators, artists and beginners can utilize many tools including channels, layers, filters, effects and more. A plethora of file formats are supported including .psd, .jpg, .gif, .png, .pdf, .hdr, .tif, .bmp and many more.
- Full program that never expires - Free for-life updates and a lifetime license. No yearly subscription or key code is required ever again!
- Multi-Platform Edition USB – Compatible with Microsoft Windows PC and Mac. You will receive the USB (not a disc) exactly as pictured, in a protective sleeve (retail box not included). Our slimline USB is 100% compatible with ALL standard-size USB ports.
- PixelClassics Bonus Content – Access to 2.7 MILLION royalty-free stock images photo repository, Installation Menu (PC only), Quick Start Guides and comprehensive User Manual PDF.
Dithering: smoother gradients, more grain
Dithering arranges pixels of nearby palette colors so that the eye averages them into an intermediate tone. The W3C specification notes that dithering is recommended for photograph-like imagery to reduce contour artifacts, and it also warns that dithering may produce graininess. In practice, dithering trades a visible step for a visible texture. Whether that trade is an improvement depends on the image and on how close the viewer is to it.
File size: no fixed reduction is guaranteed
Reducing the palette often makes a file smaller, because each pixel carries a smaller index and the palette stores fewer entries. However, the specification does not publish a general size saving, and the actual result depends on the image content and the encoder. A gradient with dithering may compress worse than the same gradient without it, because the added pattern is harder to compress. Measure the output of your own image rather than assuming a reduction.
Quick Recap
Best Value
- ✔️ AI Upscaling up to 8K: Enlarge small, low-resolution, or old photos with crisp details, clean edges, and fewer artifacts — perfect for prints, social media, blogs, and online galleries.
- ✔️ Fix blurry or noisy photos: AI restores clarity by enhancing textures, sharpening faces, hair, and fine details while reducing noise and JPEG compression errors.
- ✔️ Ideal for family photos, scans & mobile images: Improve pictures from smartphones, tablets, digital cameras, scanners, and old archives with professional-quality results.
- ✔️ Fast & easy 1-click enhancement: Batch-process multiple photos at once and improve image quality instantly — no editing experience required.
- ✔️ Reliable results & broad file support: Works with JPG, PNG, TIFF and more — stable AI processing even on old, compressed or damaged photos.
How to check whether your conversion changed the image
- Keep the original, truecolor version of the image as the reference.
- Convert it to indexed color with your chosen palette size and dithering setting, and save the result as a new file.
- Compare the two images with a pixel-difference tool or a side-by-side view at 100 percent zoom. Pay attention to gradients and to any edge where colors meet.
- If the differences are not acceptable, increase the palette size, switch dithering off or on, or keep the image in a truecolor PNG.
Practical rules
- A PNG that you encode from a source using fewer distinct colors than the palette holds is exact.
- Reducing an image with more colors than the palette holds is quantization, and it changes pixels.
- Keep an unreduced master file if you may need the original colors later, because a reduced PNG cannot recover the colors it discarded.
- Choose the palette size and dithering setting by looking at the output of the actual image, not by a general rule.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
