Document encoder quality setting more explicitly (WAS: quality 10 damages color)

[tomlarkworthy]

I have a red square on a green background. With quality 10 the red square is draw black. With quality 1, it is fine. I assumed quality 10 was the highest, although the readme is somewhat vague on what that parameter does.

[janajri]

@tomlarkworthy, I also thought 1 meant worse quality but taking a look at the code you'll see otherwise: https://github.com/eugeneware/gifencoder/blob/master/lib/GIFEncoder.js#L226

[sustained]

Just ran into this issue myself, what a strange choice to make 1 the "highest"!

[heikkipora]

Value range for setQuality is actually 1 - 30. This is directly defined by the color quantization algorithms.

setQuality() code comment says:

Sets quality of color quantization (conversion of images to the maximum 256
colors allowed by the GIF specification). Lower values (minimum = 1)
produce better colors, but slow processing significantly. 10 is the
default, and produces good color mapping at reasonable speeds. Values
greater than 20 do not yield significant improvements in speed.

NeueQuant constructor code comment says:

samplefac - sampling factor 1 to 30 where lower is better quality

TODO: Document at README level

[dmitryshelomanov]

@heikkipora is it possible to hand the encoder multiple base64 image and transform to gif ? (without canvas, only base64 array)

[heikkipora]

@userbq201: Unfortunately, no. Quote from the README.md: "The chunks that get emitted by your read stream must either by a 1-dimensional bitmap of RGBA data (either an array or Buffer), or a canvas 2D context."
This means you have to decode your base64 encoding and then decode whatever format your images are in - and pass the data as raw RGBA data to the GIF encoder.
The GIF encoder doesn't support any decoding (anyway, it's an encoder.. :-) )

[dmitryshelomanov]

@heikkipora jpg in array will suit ?

[heikkipora]

@userbq201 your JPGs needs to be decoded to raw pixels (32bit rgba) before passing to the encoder

[JohnForster]

It would be nice if this info was in the readme

[danielo515]

I also vote for documenting this. Other derived libraries that use this one doesn't include the meaning either, so it is a chain of confusion