Function prepareGrids

docs/app/js/sanddance-app.js:105780–105801

(imgData, width, height, glyphWidth, glyphHeight, gridOuter, gridInner)

    this.middle = Math.round(size / 2 * (navigator.userAgent.indexOf("Gecko/") >= 0 ? 1.2 : 1));
}
function prepareGrids(imgData, width, height, glyphWidth, glyphHeight, gridOuter, gridInner) {
    // Initialize grids outside the glyph range to alpha 0
    gridOuter.fill(INF, 0, width * height);
    gridInner.fill(0, 0, width * height);
    var offset = (width - glyphWidth) / 2; // This is zero if we're not extracting metrics
    for(var y = 0; y < glyphHeight; y++)for(var x = 0; x < glyphWidth; x++){
        var j = (y + offset) * width + x + offset;
        var a = imgData.data[4 * (y * glyphWidth + x) + 3] / 255; // alpha value
        if (a === 1) {
            gridOuter[j] = 0;
            gridInner[j] = INF;
        } else if (a === 0) {
            gridOuter[j] = INF;
            gridInner[j] = 0;
        } else {
            var b = Math.max(0, 0.5 - a);
            var c = Math.max(0, a - 0.5);
            gridOuter[j] = b * b;
            gridInner[j] = c * c;
        }
    }
}
function extractAlpha(alphaChannel, width, height, gridOuter, gridInner, radius, cutoff) {
    for(var i = 0; i < width * height; i++){
        var d = Math.sqrt(gridOuter[i]) - Math.sqrt(gridInner[i]);