source: other-projects/nz-flag-design/trunk/similarity-2d/flag-processing.js@ 29626

var progressVal = 0;

var show_progress = 5;

var timeout_delay = 100;

function drawImage(imageObj, canvasId) {
    "use strict";
    var imgCanvas = document.getElementById(canvasId),
        context, imageData, data,
        imageX = 0, imageY = 0,
        imageWidth = imageObj.width,
        imageHeight = imageObj.height;

    context = imgCanvas.getContext('2d');
    context.drawImage(imageObj, imageX, imageY, imageWidth, imageHeight);
    imageData = context.getImageData(imageX, imageY, imageWidth, imageHeight);

    return imageData;
}

function createHSLHistogram(imageObj, quant)
{
    var i;

    if (!$('#hsl_canvas').length) {
    $('<canvas>', {id: 'hsl_canvas'}).hide().appendTo('body');
    }

    imageData = drawImage(imageObj,'hsl_canvas');

    var outputLength = quant * quant * quant;
    var outputArray = new Array(outputLength);
    for (i=0; i<outputLength; i++) {
    outputArray[i] = 0;
    }

    var total = 0.0;
            
    var log2 = Math.log(2);

    //calculate value to shift by (log base 2)
        
    var shift_sat = Math.floor(Math.log(quant)/log2);
    var shift_hue = Math.floor(Math.log(quant*quant)/log2);

    //console.log("bit-shift sat = " + shift_sat);
    //console.log("bit-shift hue = " + shift_hue);

    var data = imageData.data;

    //Loop through each pixel
    var y,p;
    for (y=0,p=0; y<imageObj.height; y++) {
    var x;
    for (x=0; x<imageObj.width; x++,p+=4) {
        // convert 4 byte data value into a colour pixel
        var rgb_c = new RGBColour(data[p],data[p+1],data[p+2],data[p+3]/255.0);
        var hsl = new rgb_c.getHSL();

        // express h,s and b in the range 0..1

        var h = hsl.h / 360.0;
        var s = hsl.s / 100.0;
        var b = hsl.l / 100.0;
        
        var result =    (Math.floor(h * (quant - 1)) << shift_hue) 
                  | (Math.floor(s * (quant - 1)) << shift_sat) 
                  |  Math.floor(b * (quant - 1));

        //number of opaque pixels
        var count = hsl.a;  // 'a' is naturally in the range 0..1
            
        //add to the total number of opaque pixels
        total += count;

        //add the frequency of each colour to the histogram
        outputArray[result] += count;                    
    }
    }

    //Normalise the histogram, based on the number of opaque pixels
    for (i=0; i<outputArray.length; i++) {
    outputArray[i] = outputArray[i] / total;
    }

    return outputArray;
}

var flag_comparison_array = Array(2);
var clicked_on_count = 0;

function quantizedColourHistogramComparison(quant_colour_hist1,quant_colour_hist2) 
{
    // Assumes both histograms are of the same length

    var i;
    var quant_product = 0.0;

    //Loop through and compare the histograms
    for (i=0; i<quant_colour_hist1.length; i++) {
    //take the overlap
    quant_product += Math.min(quant_colour_hist1[i], quant_colour_hist2[i]);

    // consider replacing with abs for difference
    }

    alert("Product for HSL histogram: " + quant_product);

}


function displayFlags(img_list,$displayDiv,$progressArea,$progressBar)
{
    var img_list_len = img_list.length;

    if (img_list_len==0) {
    return;
    }
    else if (img_list_len>show_progress) {
    $progressArea.slideDown();
    }

    var root_img_re = /^.*\/(.*?)\..*?$/;

    var progress_step = 100.0 / img_list_len;
    
    var callback_count = 0;
    
    var i;
    for (i=0; i<img_list.length; i++) {
    var img_url     = img_list[i];
    var img_matches = root_img_re.exec(img_url);
    var title       = img_matches[1];
    
    var imageObj = new Image();
    imageObj.onload = function() {
        callback_count++;
        progressVal += progress_step;   
        $progressBar.progressbar('value',progressVal);
        
        if (callback_count == img_list_len) {
        if (img_list_len>show_progress) {
            progressVal = 100;
            $progressBar.progressbar('value',progressVal);
            //$progressArea.slideUp();

            // Now move on and start computing colour histograms
            setTimeout(function() 
                   {  computeFlagHistograms(img_list,$progressArea,$progressBar); }
                   ,timeout_delay);
        }
        }
    };

    imageObj.onclick = function() {
        // Store result of HSL quantization in the image object/tag
        if (!this.quantHSLHist) {
        // Only need to compute this if it is not already stored in the object/tag
        this.quantHSLHist = createHSLHistogram(this,16);
        console.log(this.quantHSLHist);
        }
        flag_comparison_array[clicked_on_count] = this.quantHSLHist;

        clicked_on_count++;
        if (clicked_on_count==2) {
        // trigger comparison
        quantizedColourHistogramComparison(flag_comparison_array[0],flag_comparison_array[1]);
        clicked_on_count=0;
        }
    };
    
    
    imageObj.src   = img_url;
    imageObj.title = title;
    imageObj.id    = "flag-img-" + i;

    $displayDiv.append(imageObj);
    }
}

function computeFlagHistogramChain(chain_count, img_list_len,
                   progressVal, progress_step,
                   $progressArea,$progressBar)
{
    var flag_id = "flag-img-" + chain_count;
    console.log("Processing Image ID: " + flag_id);
    var imageObj = document.getElementById(flag_id);

    if (!imageObj.quantHSLHist) {
    // Only need to compute this if it is not
    // already stored in the object/tag
    imageObj.quantHSLHist = createHSLHistogram(imageObj,16);
    //console.log(imageObj.quantHSLHist);
    }

    if (chain_count < img_list_len-1) {
    progressVal += progress_step;   
    $progressBar.progressbar('value',progressVal);

    setTimeout(function()
           { computeFlagHistogramChain(chain_count+1,img_list_len,
                           progressVal, progress_step,
                           $progressArea,$progressBar)
               }
           ,timeout_delay // any time delay causes break in 'rendering' thread, even 0!
           );

    }
    else {
    $progressArea.find('span:first').text("Done.");
    if (img_list_len>show_progress) {
        progressVal = 100;
        $progressBar.progressbar('value',progressVal);
        $progressArea.slideUp();
    }
    }
}

function computeFlagHistograms(img_list,$progressArea,$progressBar)
{
    var img_list_len = img_list.length;


    if (img_list_len==0) {
    $progressArea.find('span:first').text("Empty list: no computation needed.");
    return;
    }

    $progressArea.find('span:first').text("Computing histograms:");
    progressVal = 0;

    if (img_list_len>show_progress) {
    $progressArea.slideDown();
    }

    var progress_step = 100.0 / img_list_len;
 
    // Start the chaining process
    setTimeout(function() 
           { computeFlagHistogramChain(0,img_list_len,
                       progressVal, progress_step,
                       $progressArea,$progressBar)
               }
           ,timeout_delay // any time delay causes break in 'rendering' thread, even 0!
           );
    
}