canvasutil

node-canvasutil

this is a module designed to provide a lib of color space conversion functions and to provide filters for transforming pixels in a canvas image data array in wierd, fun, and useful ways.

api

PixelCore pixel core is the core object used to apply transforms on a canvas.

this is a standard object so extend it as you need =)

var PixelCore = require('canvasutil').PixelCore
, pixelProcessor = new PixelCore();

this is the only method defined in the prototype of PixelCore it accepts a node canvas as arg 1 and a transform callback as arg 2

pixelProcessor.iterate(Canvas,eachPixelCallback);

this is a value that may be used in transform callbacks that have a scaling behavior

pixelProcessor.threshold = 50;

the transforms object is a convience property to hold all available transform methods

pixelProcessor.transforms

this holds all grayscale flavors of transforms

pixelProcessor.transforms.grayscale
//the best grayscale transform is luma so use that one unless you have a specific need
pixelProcessor.transforms.grayscale.luma

and i have some other interesting transforms

//brightens everything below a threshold to threshold
//threshold range is 0-100
pixelProcessor.transforms.brightenThreshold

//whitens any pixel with a saturation greater than threshold
//threshold range is 0-100
pixelProcessor.transforms.saturationThreshold

//dims any pixel with a Luma greater than threshold. this is not the same as adding black
//threshold range is 0-255
pixelProcessor.transforms.dimThreshold

//lighten any pixel with a Luma less than threshold. this is not the same as adding white
//threshold range is 0-255
pixelProcessor.transforms.lightenThreshold

conversionLib conversion lib has all of the color space conversion functions.

all of these function exports take 3 arguments that are the 3 components of their colorspace all of these function return and array with the 3 components of the new color space

rgbToHsl(r,g,b)
hslToRgb(h.s.l)
rgbToHsv(r,g,b)
hsvToRgb(h,s,v)
rgbToYuv(r,g,b)
yuvToRgb(y,u,v)

this accepts r,g,b like the others bvut only returns the Y component of YUV

luma709Only(r,g,b)

i welcome pull requests for other helper methods for color conversion, opacity to color, hex to rgb etc. i feel that this is where they belong... for now =)

example

var Canvas = require('canvas')
, canvas = new Canvas(100,100)
,pxCore = new require('canvasutil').PixelCore;
,img = new Canvas.Image();

img.onload(function(){
	var ctx = canvas.getContext('2d');
	ctx.drawImage(img,0,0);

	pxCore.threshold = 30;
	pxCore.itterate(canvas,pxCore.transforms.brightenThreshold);

	canvas.toDataURL(function(err,url){
		console.log(url);
	});
});
img.src = "some path to an image";