Pixels And Art Glossary

[AlexHW]

My understanding is that Dichromatic gradient is one that translates from one color to another, since Di means two. Then there's Trichromatic(three different colors on a colorwheel). Polychromatic means multiple colors, and generally refers to images that use multiple colors. I suppose you could have a polychromatic gradient, but this would involve basically two dichromatic gradient stuck together? I learnt about monochromatic gradients and achromatic gradients in general art before I learnt about pixel-art, so I'm more attached to that way of classifying things and might be a way to bridge things with general art.
They are classed under the types of Value Scales.
Also, one thing I'm unsure about is whether there is a better term for gradients that begin with a strong color and transition to an achromatic color. Because achromatic gradients tend to refer to gradients that lack any color/hue, even though you could probably put colors that are near grey into it and still call it achromatic (because there are achromatic colors).

[Ai]

It looks like possibly Alex meant a different thing by 'monochromatic' gradient than my interpretation. Typically I think of a monochromatic gradient as what you get if you lay down a panel of color, then use Blend tool in Multiply mode to progressively darken it with a greyscale gradient -- ie. a gradient in which all colors have the same hue and saturation.

(This doesn't always happen because blend modes and especially color spaces are imperfect, but that's the general idea)

Personally I'd be inclined to say that color -> grey or grey -> color gradients have rather marginal usefulness in pixel art. (painting and cinematics are a different story)

[AlexHW]

It looks like possibly Alex meant a different thing by 'monochromatic' gradient than my interpretation.

The way you describe it is how I'd view it.
From what I gather, adding white to a color "Tints" it. Adding black "Shades" it. Adding grey "Tones" it.
Any Dichromatic gradient basically is a shift of hue, since both ends have different hues. The Dichromatic gradient doesn't need to be tinted, shaded, or toned- but it could be?

[0xDB]

Well...

These last couple of post illustrate well how very easy it is to get lost in details and straying from the goal to provide brief descriptions. The initially provided generalization for Color Gradient/Ramp/Shift already covers all cases discussed in these last posts(not necessarily by any well known name) and serves its purpose of providing an entry point to that particular topic (and there's always the "further reading" links as well).

So there is no need for changing the general case and I'm adding the new terms provided as seperate entries, linking to existing descriptions on wikipedia. It is better to have narrower, specialized entries for individual types of gradients(or rather terms as these terms are not restricted to use in gradients) instead of overloading the elegant simplicity of the generalization with these details.

Since the goal of the Glossary is to stay descriptive in nature, giving examples for different gradients/ramps and providing an assessment/judgement of/about their usefulnes in Pixel Art is left as something for a tutorial on choosing colors, making a pallette, coming up with a color scheme (I personally have no plans at the moment to write any tutorials).

Dichromatism and Polychromatism, as researching on the web suggests, appear to already refer to a very specific phenomenon where the hue of something appears different based on thickness and concentration (e.g. the intensifaction of yellow and blue water as it shifts to a different hue as described in the Color entry). I feel that might be too specialized to be mentioned at all. Not that I think anything is irrelevant when it comes to Visual Art/Crafting but the scope of this Glossary should probably be limited or otherwise we might as well just provide a link to the Wikipedia starting page (or google) and be done with it.

these entries have been added/changed:

Achromatic Color
Literally a color "without color", which is all shades of gray and black and white.
Practically all colors without a strong perceptual chromaticity are called achromatic.
https://en.wikipedia.org/wiki/Color_scheme#Achromatic_colors
https://en.wikipedia.org/w/index.php?title=Achromatic_color&redirect=no (redirects to Grey at time of writing this)

Color
+ https://en.wikipedia.org/wiki/Complementary_colors

Color Scheme
https://en.wikipedia.org/wiki/Color_scheme

Monochromatic Color
All tints, tones and shades of equal hue.
https://en.wikipedia.org/wiki/Color_scheme#Monochromatic_colors
https://en.wikipedia.org/wiki/Monochromatic_color

[0xDB]

Most entries in the opening post now have at least a brief summary and/or links to vast amounts of information on everyones favorite open encyclopedia.

[0xDB]

Entries in opening post now have anchor and iurl tags and there is an index at the top for quickly grabbing links to individual terms.
_{(I'll eventually have to cut the duplicate text under the images because of the 50000 chars per post limit.)}

[questseeker]

I'd expect more entries about techniques and patterns found both in tools and workflows and in images. Here's a first draft of two important ones:

Pillow Shading
Unrealistic shading of a smoothly curved object by distributing light and dark colors according to the shape of the object's outline instead of imagining and matching the shape of actual isophotes and the location of highlights; this normally results in approximately parallel and constant width color bands from the outline inwards, vastly different from the bunched up, interrupted, expanded and nonconvex shapes of correct shading.
A rectangular pillow is one of the rare cases in which the incorrect but easy procedure sometimes approaches a correct result.

Index Painting
Editing palette indexes instead of pixel colors; it implies caring about palette organization (two palettes with the same colors in a different order are different) and not only about limiting the available colors.

Deliberate attention for building the final image through an explicit indirect mapping mechanism can have a variety of benefits and purposes, mostly related to determining actual colors after editing the image:

• Making images that can be displayed with different but "parallel" palettes (as typical of many videogames with recolored sprites, which can be implemented with a simple palette swap).
• Distinguishing palette indexes in order to treat identical colors as logically different, for example because they are shades in different color ramps.
• Caring about the use of palette entries rather than their actual color (e.g. "I need three entries for flesh, eyes and pupils and I'll reuse hair colors for irises" vs. "I need three entries for rosy pink, blueish white and pure black"); palette structure can be more important and more stable than the contained colors.
• Controlling palette indices exactly (as opposed to letting the paint program manage them automatically) because they also have some conventional meaning: transparency (e.g. index 0 is transparent), metadata about a game sprite such as whether a pixel is a solid part of an object, special display-time palette tricks (e.g. indexes in a certain range are subject to color cycling) and so on.
• Allowing use of tools, like semi-transparent brushes, compositing transparent layers, blurring, etc. that are fundamentally unsuitable for simple palette-based image representations. For example, editing a high bit depth greyscale image and mapping grey ranges to palette colors, as popularized by Dan Fessler (1,2).

1. http://www.danfessler.com/blog/pixel-purism-process-vs-results
2. http://www.danfessler.com/blog/hd-index-painting-in-photoshop

[0xDB]

There is already a short entry for Indexed Image/Color.

Personally, I never gave Index Painting much explicit thought because in all pixel art tools I've used (starting with PaintMagic on the C64 and DPaintIII on the Amiga500), "Index Painting" (though it was not called that back then I think, it didn't seem to have a name then) was just the default or only mode the tools and hardware(like the C64) could even handle, so to me, that was always the natural way to go/think about pixel art.

With non-indexed modes around today however, "Index Painting"(what making Pixel Art really already always was imo) should indeed be mentioned separately, but I suggest in more than just one additional entry, broken down into more specific terms:

Index Painting (broad generalization goes into that with links to Dan's articles)

Pallete Swap (full and partial swaps, with examples like faction colors in strategy games or a number of "identical" grayscales for different elements like clothes for individual partial swaps per element)

Color Cycling (a special case of a number of "Pallete Effects")

Palette Structure (logical mapping between palette indices and objects those indices will be used for (skin colors, shoe colors, ... closely related to preparing something for effects like Color Cycling and partial or full Palette Swaps)

Pallete Effects (umbrella term for things like Color Cycling, Palette Swaps, Palette Fading)

The fact, that using automated tools ( "dirty" as they're often called) which cause mutations of affected pixels by color without caring about indices, are mostly unsuitable if Palette Structure is important for programmatic effects seems obvious but maybe it should be mentioned in an entry about "'Dirty' Tools" without condemning them as forbidden though, just to point out that their usage can require manual cleanup and making sure each pixel refers to the correct palette index after applying them (seems though that this might be better covered in a tutorial about Palette Structure as it's pretty longwinding for a brief description which aims to be free of judgement).

...

Added example and fleshed out description to the existing Pillow Shading entry:

[0xDB]

Added entries for Palette Effect, Palette Structure and Palette Swap.

---

Palette Effect
In Indexed Images/Modes where each pixel in the image refers to a specific color in a sequence of colors(=palette) (instead of holding the full definition of the color in each individual pixel itself), a number of visual effects such as Color Cycling and Color Fading can be achieved by manipulating the palette instead of manipulating the pixels themselves.

This was used a lot on old hardware as manipulating the definition of colors in the palette took much fewer CPU cycles than going through the image and changing the actual pixels themselves.

A simple example for a Palette Effect is just re-defining a color in the palette:
If a thousand pixels in an image referred to color at index five in the palette and index five would hold Green and index twelve would hold Red, all thousand pixels could be changed to Red by changing the color at index five from Green to Red instead of going through the image and looking for every Green pixel and changing the pixel itself to refer to index twelve.


Palette Structure



Palette Swap

[0xDB]

Added History Of Pixel Art, Index Painting and Color Cycling.


History Of Pixel Art
see The History Of Pixel Art


Index Painting
Creating Pixel Art in Indexed Modes, working with Indexed Images while paying attention to Palette Structure and keeping possible Palette Effects in mind and at all times keeping control over (if necessary by fixing the results) the pixel level polish of a piece even when using tools that influence more than one pixel at a time.

Historically, "Index Painting" is the natural way to go and think about making Pixel Art as most hardware and digital image editing tools either used Indexed Modes as the default mode or simply did not provide any other modes. The term "Index Painting" was not around then because there simply was nothing else. Today the term seems to be used to set "Pixel Art"(in the sense of Index Painting) apart from other "Pixel Art"(in the sense of Digital Painting and Computer Generated Imagery(e.g. 3D renderings)) and the third kind of "Pixel Art"(the purists "one pixel at a time"- process).

Some advocate placing one pixel at a time as the only "allowed" process to create "Pixel Art"(a term which eludes definition itself) while others advocate whether something is or is not "Pixel Art" can not be defined by processes but only by looking at the results.

The actual term "Index Painting" emerged from the on-going online debate about "pixel purism", processes and results:
http://www.danfessler.com/blog/pixel-purism-process-vs-results
http://www.danfessler.com/blog/hd-index-painting-in-photoshop


Palette Swap - Color Cycling

further reading:
https://en.wikipedia.org/wiki/Color_cycling