Some of these pixel art techniques are taken from the Pixel Logic book. The book is highly recommended.
On resizing artwork
Always resize in numbers that return a number without infinite decimals:
100%:200% = 0.5
100%:400% = 0.25
100%:800% = 0.125
100%:1000% = 0.1
This way, your artwork can be scaled down to the original resolution without messing up the pixels.
Types of Outlines-Inlines
It’s a black outline that goes inside the sprite sometimes.
It’s a black outline that doesn’t go inside the sprite.
The outline takes a darker tone than the one inside the sprite.
The outline is affected by the light.
It goes from darker to lighter, too much of it could make your art look blurry.
It can be used to blend highly contrasting colors, or to make lines appear thicker or thinner. It’s also useful to smooth jagged lines. The longer a line is, the longer the AA.
AA edges can also be jaggy, that’s something to look out for, keep a pattern between the different shades of AA, as they were common outlines.
Lighter = Thin
Darker = Thick
Lighter color = add more to each value.
Grays = same value for all three components.
Dull colors = values close together.
Richer colors = values far from each other.
From Pixel Logic.
There are multiple combinations that you can use, you can shift the hue from left to right, or make the shadows more saturated, or duller, or the highlights more saturated, or duller. You can also choose how much you want to shift the hue, and shift the saturation, it’s mostly a matter of style and what you feel looks nicer in that specific assets or style.
In general, I try to avoid pure black and pure white, although it also depends on the style that you’re going for, for outlines, I prefer to use a dark color instead of pure black, again, depending on the style.
When mixing two complementary colors, you ‘neutralize’ them, bringing the result to an almost perfect gray.
A gray over a cold background, will be perceived warm, a gray over a warm background, will be perceived cold.
When drawing in a really small resolution, it might be better to draw with shapes instead of lines, then you can polish the shape and detail them.
On hands, the thumb and index makes the hand readable.
Zooming out and blurring the image are great ways to see if your image is readable.
Above are the different patterns, darker in the center.
Avoid using dithering on small pieces, avoid using dithering in animation, as it would take too long to make it look nice.
The lower the contrast between tones, the softer the dithering.
You can also dither with vertical, horizontal lines, discontinued lines, and any other kind of pattern.
Those are some pixel art techniques, sometime in the future others like sub-pixel animation might appear in the blog.