plot.js

/**
* Copyright 2012-2018, Plotly, Inc.
* All rights reserved.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/


'use strict';

var tinycolor = require('tinycolor2');

var Registry = require('../../registry');
var Lib = require('../../lib');
var Colorscale = require('../../components/colorscale');
var xmlnsNamespaces = require('../../constants/xmlns_namespaces');

var maxRowLength = require('./max_row_length');


module.exports = function(gd, plotinfo, cdheatmaps) {
    for(var i = 0; i < cdheatmaps.length; i++) {
        plotOne(gd, plotinfo, cdheatmaps[i]);
    }
};

function plotOne(gd, plotinfo, cd) {
    var cd0 = cd[0];
    var trace = cd0.trace;
    var uid = trace.uid;
    var xa = plotinfo.xaxis;
    var ya = plotinfo.yaxis;
    var fullLayout = gd._fullLayout;
    var id = 'hm' + uid;

    // in case this used to be a contour map
    fullLayout._paper.selectAll('.contour' + uid).remove();
    fullLayout._infolayer.selectAll('g.rangeslider-container')
        .selectAll('.contour' + uid).remove();

    if(trace.visible !== true) {
        fullLayout._paper.selectAll('.' + id).remove();
        fullLayout._infolayer.selectAll('.cb' + uid).remove();
        return;
    }

    var z = cd0.z;
    var x = cd0.x;
    var y = cd0.y;
    var xc = cd0.xCenter;
    var yc = cd0.yCenter;
    var isContour = Registry.traceIs(trace, 'contour');
    var zsmooth = isContour ? 'best' : trace.zsmooth;

    // get z dims
    var m = z.length;
    var n = maxRowLength(z);
    var xrev = false;
    var yrev = false;

    var left, right, temp, top, bottom, i;

    // TODO: if there are multiple overlapping categorical heatmaps,
    // or if we allow category sorting, then the categories may not be
    // sequential... may need to reorder and/or expand z

    // Get edges of png in pixels (xa.c2p() maps axes coordinates to pixel coordinates)
    // figure out if either axis is reversed (y is usually reversed, in pixel coords)
    // also clip the image to maximum 50% outside the visible plot area
    // bigger image lets you pan more naturally, but slows performance.
    // TODO: use low-resolution images outside the visible plot for panning
    // these while loops find the first and last brick bounds that are defined
    // (in case of log of a negative)
    i = 0;
    while(left === undefined && i < x.length - 1) {
        left = xa.c2p(x[i]);
        i++;
    }
    i = x.length - 1;
    while(right === undefined && i > 0) {
        right = xa.c2p(x[i]);
        i--;
    }

    if(right < left) {
        temp = right;
        right = left;
        left = temp;
        xrev = true;
    }

    i = 0;
    while(top === undefined && i < y.length - 1) {
        top = ya.c2p(y[i]);
        i++;
    }
    i = y.length - 1;
    while(bottom === undefined && i > 0) {
        bottom = ya.c2p(y[i]);
        i--;
    }

    if(bottom < top) {
        temp = top;
        top = bottom;
        bottom = temp;
        yrev = true;
    }

    // for contours with heatmap fill, we generate the boundaries based on
    // brick centers but then use the brick edges for drawing the bricks
    if(isContour) {
        xc = x;
        yc = y;
        x = cd0.xfill;
        y = cd0.yfill;
    }

    // make an image that goes at most half a screen off either side, to keep
    // time reasonable when you zoom in. if zsmooth is true/fast, don't worry
    // about this, because zooming doesn't increase number of pixels
    // if zsmooth is best, don't include anything off screen because it takes too long
    if(zsmooth !== 'fast') {
        var extra = zsmooth === 'best' ? 0 : 0.5;
        left = Math.max(-extra * xa._length, left);
        right = Math.min((1 + extra) * xa._length, right);
        top = Math.max(-extra * ya._length, top);
        bottom = Math.min((1 + extra) * ya._length, bottom);
    }

    var imageWidth = Math.round(right - left),
        imageHeight = Math.round(bottom - top);

    // setup image nodes

    // if image is entirely off-screen, don't even draw it
    var isOffScreen = (imageWidth <= 0 || imageHeight <= 0);

    var plotgroup = plotinfo.plot.select('.imagelayer')
        .selectAll('g.hm.' + id)
        .data(isOffScreen ? [] : [0]);

    plotgroup.enter().append('g')
        .classed('hm', true)
        .classed(id, true);

    plotgroup.exit().remove();

    if(isOffScreen) return;

    // generate image data

    var canvasW, canvasH;
    if(zsmooth === 'fast') {
        canvasW = n;
        canvasH = m;
    } else {
        canvasW = imageWidth;
        canvasH = imageHeight;
    }

    var canvas = document.createElement('canvas');
    canvas.width = canvasW;
    canvas.height = canvasH;
    var context = canvas.getContext('2d');

    var sclFunc = Colorscale.makeColorScaleFunc(
        Colorscale.extractScale(
            trace.colorscale,
            trace.zmin,
            trace.zmax
        ),
        { noNumericCheck: true, returnArray: true }
    );

    // map brick boundaries to image pixels
    var xpx,
        ypx;
    if(zsmooth === 'fast') {
        xpx = xrev ?
            function(index) { return n - 1 - index; } :
            Lib.identity;
        ypx = yrev ?
            function(index) { return m - 1 - index; } :
            Lib.identity;
    }
    else {
        xpx = function(index) {
            return Lib.constrain(Math.round(xa.c2p(x[index]) - left),
                0, imageWidth);
        };
        ypx = function(index) {
            return Lib.constrain(Math.round(ya.c2p(y[index]) - top),
                0, imageHeight);
        };
    }

    // build the pixel map brick-by-brick
    // cruise through z-matrix row-by-row
    // build a brick at each z-matrix value
    var yi = ypx(0);
    var yb = [yi, yi];
    var xbi = xrev ? 0 : 1;
    var ybi = yrev ? 0 : 1;
    // for collecting an average luminosity of the heatmap
    var pixcount = 0;
    var rcount = 0;
    var gcount = 0;
    var bcount = 0;

    var xb, j, xi, v, row, c;

    function setColor(v, pixsize) {
        if(v !== undefined) {
            var c = sclFunc(v);
            c[0] = Math.round(c[0]);
            c[1] = Math.round(c[1]);
            c[2] = Math.round(c[2]);

            pixcount += pixsize;
            rcount += c[0] * pixsize;
            gcount += c[1] * pixsize;
            bcount += c[2] * pixsize;
            return c;
        }
        return [0, 0, 0, 0];
    }

    function interpColor(r0, r1, xinterp, yinterp) {
        var z00 = r0[xinterp.bin0];
        if(z00 === undefined) return setColor(undefined, 1);

        var z01 = r0[xinterp.bin1],
            z10 = r1[xinterp.bin0],
            z11 = r1[xinterp.bin1],
            dx = (z01 - z00) || 0,
            dy = (z10 - z00) || 0,
            dxy;

        // the bilinear interpolation term needs different calculations
        // for all the different permutations of missing data
        // among the neighbors of the main point, to ensure
        // continuity across brick boundaries.
        if(z01 === undefined) {
            if(z11 === undefined) dxy = 0;
            else if(z10 === undefined) dxy = 2 * (z11 - z00);
            else dxy = (2 * z11 - z10 - z00) * 2 / 3;
        }
        else if(z11 === undefined) {
            if(z10 === undefined) dxy = 0;
            else dxy = (2 * z00 - z01 - z10) * 2 / 3;
        }
        else if(z10 === undefined) dxy = (2 * z11 - z01 - z00) * 2 / 3;
        else dxy = (z11 + z00 - z01 - z10);

        return setColor(z00 + xinterp.frac * dx + yinterp.frac * (dy + xinterp.frac * dxy));
    }

    if(zsmooth) { // best or fast, works fastest with imageData
        var pxIndex = 0,
            pixels;

        try {
            pixels = new Uint8Array(imageWidth * imageHeight * 4);
        }
        catch(e) {
            pixels = new Array(imageWidth * imageHeight * 4);
        }

        if(zsmooth === 'best') {
            var xForPx = xc || x;
            var yForPx = yc || y;
            var xPixArray = new Array(xForPx.length);
            var yPixArray = new Array(yForPx.length);
            var xinterpArray = new Array(imageWidth);
            var findInterpX = xc ? findInterpFromCenters : findInterp;
            var findInterpY = yc ? findInterpFromCenters : findInterp;
            var yinterp, r0, r1;

            // first make arrays of x and y pixel locations of brick boundaries
            for(i = 0; i < xForPx.length; i++) xPixArray[i] = Math.round(xa.c2p(xForPx[i]) - left);
            for(i = 0; i < yForPx.length; i++) yPixArray[i] = Math.round(ya.c2p(yForPx[i]) - top);

            // then make arrays of interpolations
            // (bin0=closest, bin1=next, frac=fractional dist.)
            for(i = 0; i < imageWidth; i++) xinterpArray[i] = findInterpX(i, xPixArray);

            // now do the interpolations and fill the png
            for(j = 0; j < imageHeight; j++) {
                yinterp = findInterpY(j, yPixArray);
                r0 = z[yinterp.bin0];
                r1 = z[yinterp.bin1];
                for(i = 0; i < imageWidth; i++, pxIndex += 4) {
                    c = interpColor(r0, r1, xinterpArray[i], yinterp);
                    putColor(pixels, pxIndex, c);
                }
            }
        }
        else { // zsmooth = fast
            for(j = 0; j < m; j++) {
                row = z[j];
                yb = ypx(j);
                for(i = 0; i < imageWidth; i++) {
                    c = setColor(row[i], 1);
                    pxIndex = (yb * imageWidth + xpx(i)) * 4;
                    putColor(pixels, pxIndex, c);
                }
            }
        }

        var imageData = context.createImageData(imageWidth, imageHeight);
        try {
            imageData.data.set(pixels);
        }
        catch(e) {
            var pxArray = imageData.data,
                dlen = pxArray.length;
            for(j = 0; j < dlen; j ++) {
                pxArray[j] = pixels[j];
            }
        }

        context.putImageData(imageData, 0, 0);
    } else { // zsmooth = false -> filling potentially large bricks works fastest with fillRect

        // gaps do not need to be exact integers, but if they *are* we will get
        // cleaner edges by rounding at least one edge
        var xGap = trace.xgap;
        var yGap = trace.ygap;
        var xGapLeft = Math.floor(xGap / 2);
        var yGapTop = Math.floor(yGap / 2);

        for(j = 0; j < m; j++) {
            row = z[j];
            yb.reverse();
            yb[ybi] = ypx(j + 1);
            if(yb[0] === yb[1] || yb[0] === undefined || yb[1] === undefined) {
                continue;
            }
            xi = xpx(0);
            xb = [xi, xi];
            for(i = 0; i < n; i++) {
                // build one color brick!
                xb.reverse();
                xb[xbi] = xpx(i + 1);
                if(xb[0] === xb[1] || xb[0] === undefined || xb[1] === undefined) {
                    continue;
                }
                v = row[i];
                c = setColor(v, (xb[1] - xb[0]) * (yb[1] - yb[0]));
                context.fillStyle = 'rgba(' + c.join(',') + ')';

                context.fillRect(xb[0] + xGapLeft, yb[0] + yGapTop,
                    xb[1] - xb[0] - xGap, yb[1] - yb[0] - yGap);
            }
        }
    }

    rcount = Math.round(rcount / pixcount);
    gcount = Math.round(gcount / pixcount);
    bcount = Math.round(bcount / pixcount);
    var avgColor = tinycolor('rgb(' + rcount + ',' + gcount + ',' + bcount + ')');

    gd._hmpixcount = (gd._hmpixcount||0) + pixcount;
    gd._hmlumcount = (gd._hmlumcount||0) + pixcount * avgColor.getLuminance();

    var image3 = plotgroup.selectAll('image')
        .data(cd);

    image3.enter().append('svg:image').attr({
        xmlns: xmlnsNamespaces.svg,
        preserveAspectRatio: 'none'
    });

    image3.attr({
        height: imageHeight,
        width: imageWidth,
        x: left,
        y: top,
        'xlink:href': canvas.toDataURL('image/png')
    });

    image3.exit().remove();
}

// get interpolated bin value. Returns {bin0:closest bin, frac:fractional dist to next, bin1:next bin}
function findInterp(pixel, pixArray) {
    var maxBin = pixArray.length - 2;
    var bin = Lib.constrain(Lib.findBin(pixel, pixArray), 0, maxBin);
    var pix0 = pixArray[bin];
    var pix1 = pixArray[bin + 1];
    var interp = Lib.constrain(bin + (pixel - pix0) / (pix1 - pix0) - 0.5, 0, maxBin);
    var bin0 = Math.round(interp);
    var frac = Math.abs(interp - bin0);

    if(!interp || interp === maxBin || !frac) {
        return {
            bin0: bin0,
            bin1: bin0,
            frac: 0
        };
    }
    return {
        bin0: bin0,
        frac: frac,
        bin1: Math.round(bin0 + frac / (interp - bin0))
    };
}

function findInterpFromCenters(pixel, centerPixArray) {
    var maxBin = centerPixArray.length - 1;
    var bin = Lib.constrain(Lib.findBin(pixel, centerPixArray), 0, maxBin);
    var pix0 = centerPixArray[bin];
    var pix1 = centerPixArray[bin + 1];
    var frac = ((pixel - pix0) / (pix1 - pix0)) || 0;
    if(frac <= 0) {
        return {
            bin0: bin,
            bin1: bin,
            frac: 0
        };
    }
    if(frac < 0.5) {
        return {
            bin0: bin,
            bin1: bin + 1,
            frac: frac
        };
    }
    return {
        bin0: bin + 1,
        bin1: bin,
        frac: 1 - frac
    };
}

function putColor(pixels, pxIndex, c) {
    pixels[pxIndex] = c[0];
    pixels[pxIndex + 1] = c[1];
    pixels[pxIndex + 2] = c[2];
    pixels[pxIndex + 3] = Math.round(c[3] * 255);
}