Websites should not use dithered images • Hacker News Board

Re: Websites should not use dithered images

#131

Post by devit » Tue, Nov 16, 2021, 2:54 AM UTC

anentropic wrote: post #67

Wow I feel old, everyone seems to have forgotten why and how to use these techniques :( No one was dithering large photos back in the day - that's what JPEG are for. The point of dithering was to take advantage of the reduced bit depth of indexed-colour GIFs (and later PNGs). The Dither-Me-This tool does a lovely job of rendering different dither styles but then misses the point completely by exporting 32-bit RGB+alp…

The point of dithering was simply that old graphics cards (e.g. VGA) only supported 16 or 256 colors.

Re: Websites should not use dithered images

#132

Post by duped » Tue, Nov 16, 2021, 6:43 AM UTC

omegalulw wrote: post #130

duped wrote: post #62

Earlier quoted context omitted.

> Dithering is a technique which allows you to represent a color image with a very limited palette, in particular a two bit palette. To be way more pedantic, dithering is a technique to reduce the quantization error (what happens when you map values from a big, possibly infinite set to a smaller, finite set). This is done whenever a system or algorithm converts data from higher dynamic range representation (more bits…

> This is done whenever a system or algorithm converts data from higher dynamic range representation (more bits per quantum of signal, like a pixel or audio sample) to a lower dynamic range representation, it's called a bit-depth reduction. You are mixing two things here? Bit depth reduction is a specific term, it refers to the reduction in the amount of information you want to _convey_. Compression is be reducing th…

I took care not to conflate the two and to isolate the terms outside the context of compression, and image processing at large.

Re: Websites should not use dithered images

#133

Post by anentropic » Tue, Nov 16, 2021, 11:43 AM UTC

devit wrote: post #131

anentropic wrote: post #67

Wow I feel old, everyone seems to have forgotten why and how to use these techniques :( No one was dithering large photos back in the day - that's what JPEG are for. The point of dithering was to take advantage of the reduced bit depth of indexed-colour GIFs (and later PNGs). The Dither-Me-This tool does a lovely job of rendering different dither styles but then misses the point completely by exporting 32-bit RGB+alp…

The point of dithering was simply that old graphics cards (e.g. VGA) only supported 16 or 256 colors.

Use of indexed-colour GIFs persisted long after better displays became commonplace, as an optimisation technique for reducing the file size of graphics for web pages