WebWorldWind/examples/CanvasWorker.js

/*
 * Copyright (C) 2014 United States Government as represented by the Administrator of the
 * National Aeronautics and Space Administration. All Rights Reserved.
 */

// Set RGBA values for a pixel
function setPixel(imageData, x, y, r, g, b, a) {
    var index = (x + y * imageData.width) * 4;
    imageData.data[index+0] = r;
    imageData.data[index+1] = g;
    imageData.data[index+2] = b;
    imageData.data[index+3] = a;
}

// Set ImageData for the canvas
function setImageData(dataArray, imageData, colorPaletteArray, regionName, filename, noDataValue)
{
    var newDataArray = [];
    for (var rowNo = 0; rowNo < dataArray.length; rowNo++)
    {
        var col = dataArray[rowNo].trim().split(' ');
        if(col.length > 1){
            for (var colNo = 0; colNo < col.length; colNo++){
                newDataArray.push(col[colNo]);
                var r, g, b, a;
                if (col[colNo] == noDataValue || col[colNo] == 255){
                    r = colorPaletteArray[2] * 255;
                    g = colorPaletteArray[3] * 255;
                    b = colorPaletteArray[4] * 255;
                    a = colorPaletteArray[5] * 255;
                    setPixel(imageData, colNo, rowNo, r, g, b, a);
                }
                else{
                    for (var k = 0; k < colorPaletteArray.length; k+=6){
                        if (col[colNo] >= colorPaletteArray[k] && col[colNo] <= colorPaletteArray[k+1])
                        {
                            r = colorPaletteArray[k+2] * 255;
                            g = colorPaletteArray[k+3] * 255;
                            b = colorPaletteArray[k+4] * 255;
                            a = colorPaletteArray[k+5] * 255;
                            setPixel(imageData, colNo, rowNo, r, g, b, a);
                            break;
                        }
                    }
                }
            }
        }
    }

    self.postMessage(
        {
            'imageData' : imageData,
            'regionName' : regionName,
            'filename' : filename,
            'dataArray' : newDataArray
        });

    imageData = null;
}

self.onmessage = function(e) {
    var imageData = e.data.imageData;
    var dataArray = e.data.dataArray;
    var colorPaletteArray = e.data.colorPaletteArray;
    var regionName = e.data.regionName;
    var filename = e.data.filename;
    var noDataValue = e.data.noDataValue;
    setImageData(dataArray, imageData, colorPaletteArray, regionName, filename, noDataValue);
}