bitmapWriter.js

Area: Raster

Demonstrates two ways to paint a bitmap: writing sparse pixels one at a time with PixelReaderWriterRGBA8 (wrapped in try/finally with w.dispose()), and filling a contiguous block fast via a PixelBuffer + Uint8Array then buffer.createCompatibleBitmap(true). The result is added as an ImageNodeDefinition with doc.addNode(nodeDef, null, undefined, preview). Directly relevant to Lesson 14, and it shows the speed trade-off between the two approaches.

Source: bitmapWriter.js

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Example scripts

bitmapWriter.js

Download bitmapWriter.js

bitmapWriter.js

/*
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modification, are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this
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this software without specific prior written permission.

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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

// Demonstrates writing bitmap using 2 methods.
// Passing true-ish to main() will use a PixelReaderWriterRGBA8 to write the pixels directly into the bitmap.
// Otherwise the data will be written into a PixelBuffer which is then copied to the bitmap.

'use strict';

const { app } = require('/application.js');
const { Dialog, DialogResult } = require('/dialog.js');
const { Document } = require('/document.js');
const { ImageNodeDefinition } = require('/nodes.js');
const { Bitmap, PixelBuffer, RasterFormat } = require('/rasterobject.js');
const { PixelReaderWriterRGBA8 } = require('/pixelaccessor.js');
const { UnitType } = require('/units.js');

function main(usePixelWriter) {
    const doc = Document.current;
    if (!doc) {
        app.alert("This example requires an open document");
        return;
    }

    const WIDTH = Math.ceil(doc.widthPixels);
    const HEIGHT = Math.ceil(doc.heightPixels);

    // Creates a Bitmap and updates its pixels using a PixelReaderWriter.
    // Useful for when a few, sparse pixels need updating.
    function createBitmapUsingPixelWriter(blue) {
        const bitmap = Bitmap.create(WIDTH, HEIGHT, RasterFormat.RGBA8);
        const w = PixelReaderWriterRGBA8.create(bitmap);
        try {
            const pixelData = { b:blue, alpha:255 };
            for(let y = 0; y < HEIGHT; ++y) {
                for(let x = 0; x < WIDTH; ++x) {
                    pixelData.r = 255*y/HEIGHT;
                    pixelData.g = 255*x/WIDTH;
                    w.writePixel(x, y, pixelData);
                }
            }
        }
        finally {
            w.dispose();
        }
        return bitmap;
    }

    // Creates a PixelBuffer, writes the pixel data to it and then copies
    // the data to a bitmap, which is then returned.
    // In general particularly for large blocks of contiguous pixels,
    // this is much faster than using a PixelReaderWriter to write the pixel data.
    function createBitmapUsingPixelBuffer(blue) {
        const buffer = PixelBuffer.create(WIDTH, HEIGHT, RasterFormat.RGBA8);
        const arr = new Uint8Array(buffer.buffer)
        let i = 0;
        for(let y = 0; y < HEIGHT; ++y) {
            for(let x = 0; x < WIDTH; ++x) {
                arr[i++] = 255*y/HEIGHT;
                arr[i++] = 255*x/WIDTH;
                arr[i++] = blue;
                arr[i++] = 255;
            }
        }
        return buffer.createCompatibleBitmap(true);
    }

    function buildDialog() {
        const dlg = Dialog.create("Bitmap Rainbow Fun");
        const col = dlg.addColumn();
        const group = col.addGroup();
        dlg.blue = group.addUnitValueEditor("Blue", UnitType.Number, UnitType.Number, 128, 0, 255)
            .setShowPopupSlider(true)
            .setPrecision(0);
        return dlg;
    }

    const dlg = buildDialog();
    const nodeDef = ImageNodeDefinition.create(RasterFormat.RGB8);
    nodeDef.userDescription = "JavaScript made this";

    function update(preview) {
        const blue = dlg.blue.value;
        nodeDef.bitmap = usePixelWriter ? createBitmapUsingPixelWriter(blue) : createBitmapUsingPixelBuffer(blue);
        doc.addNode(nodeDef, null, undefined, preview);
    }
    
    update(true);
    dlg.onControlValueChangedHandler = () => update(true);
    if (dlg.runModal() == DialogResult.Ok) {
        update(false);
    }
    else
        doc.clearPreviews();
}

module.exports.main = main;