Dithering 是一種通過像素排列模擬更多顏色的技術(shù)，用于在降低色彩深度時減少視覺損失。當(dāng)減少圖像色彩深度時，如從24位色（約1600萬色）降至8位色（僅256色），會丟失大量顏色信息，導(dǎo)致平滑漸變出現(xiàn)色帶或平坦區(qū)域；dithering 通過散布不同顏色的像素使其視覺混合，從而軟化過渡效果。其原理基于人眼將鄰近像素融合的能力，使整體視覺接近原圖，尤其適用于GIF等低色彩格式、有限色彩支持設(shè)備顯示和數(shù)字藝術(shù)風(fēng)格化。是否使用 dithering 取決于具體需求：? 使用場景包括轉(zhuǎn)換照片或復(fù)雜圖形至有限調(diào)色板、保留漸變細(xì)節(jié)、接受一定噪點(diǎn)以換取更好畫質(zhì)；? 應(yīng)避免用于清晰文字或線條藝術(shù)（可能模糊邊緣）、對文件大小敏感的情況、以及偏好干凈無紋理畫面。多數(shù)圖像編輯工具如 Photoshop、GIMP 或在線轉(zhuǎn)換器在保存 GIF 或 8-bit PNG 時提供 dithering 設(shè)置選項(xiàng)。

Dithering is a technique used in digital imaging to simulate more colors than are actually available when reducing color depth. It works by arranging pixels in patterns that trick the eye into perceiving intermediate shades that aren’t present in the reduced palette.

When you reduce an image’s color depth — say, going from millions of colors down to just 256 — you lose a lot of color information. Without dithering, this often results in visible banding or flat areas where smooth gradients once were. Dithering helps soften these transitions by scattering pixels of different colors so they blend visually.

What happens during color depth reduction?

Color depth refers to how many bits are used to represent each pixel’s color. Reducing it means fewer bits per pixel, which translates to fewer possible colors. For example:

• 24-bit color: ~16 million colors
• 8-bit color: only 256 colors

When you cut back that drastically, large areas of similar tones collapse into solid blocks. This is especially noticeable in skies, skin tones, and other smooth gradients.

Without dithering, the result can look flat or cartoonish. With dithering, those harsh edges are replaced with noise-like patterns that mimic the original variation.

How does dithering improve image appearance?

Dithering adds visual texture to otherwise flat regions. It works based on human perception — our eyes blur nearby pixels together, so even though the individual dots may not be the right color, the overall effect looks closer to the original.

This is especially useful for:

• Preserving detail in low-color formats like GIFs
• Maintaining softness in images displayed on devices with limited color support
• Creating stylized effects in digital art (some artists use dithering intentionally)

It’s worth noting that while dithering improves perceived quality, it also introduces a kind of graininess or “noise” that wasn’t there before. In some cases, especially at very small sizes or on low-resolution screens, this can be distracting.

Should you use dithering?

Whether or not to use dithering depends on your goals:

? Use dithering if:

• You’re converting photos or complex graphics to limited palettes
• You want smoother transitions in gradients
• You're okay with a bit of noise in exchange for better detail

? Avoid dithering if:

• You're working with crisp text or line art (it can blur sharp edges)
• File size matters and the added complexity increases file weight
• You prefer a clean, flat look without texture

Most image editing tools — like Photoshop, GIMP, or online converters — give you the option to enable or tweak dithering when saving in formats like GIF or 8-bit PNG.

基本上就這些。

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