function setPixel(imageInfo, r, g, b, a) {
            var imageData = imageInfo.imageData;
            var pixels = imageData.data;
            var index = imageInfo.index++ * 4;
            pixels[index++] = r;
            pixels[index++] = g;
            pixels[index++] = b;
            pixels[index++] = a;
          }
@method getGlyphInfo
@param {Glyph} glyph the x positions of points in the curve
@returns {Object} the glyphInfo for that glyph

calculates rendering info for a glyph, including the curve information,
row & column stripes compiled into textures.