Phaser Source: src/pixi/textures/RenderTexture.js

# Source: src/pixi/textures/RenderTexture.js

    /**
     * @author Mat Groves http://matgroves.com/ @Doormat23
     */

    /**
     * A RenderTexture is a special texture that allows any Pixi display object to be rendered to it.
     *
     * __Hint__: All DisplayObjects (i.e. Sprites) that render to a RenderTexture should be preloaded otherwise black rectangles will be drawn instead.
     *
     * A RenderTexture takes a snapshot of any Display Object given to its render method. The position and rotation of the given Display Objects is ignored. For example:
     *
     *    var renderTexture = new PIXI.RenderTexture(800, 600);
     *    var sprite = PIXI.Sprite.fromImage("spinObj_01.png");
     *    sprite.position.x = 800/2;
     *    sprite.position.y = 600/2;
     *    sprite.anchor.x = 0.5;
     *    sprite.anchor.y = 0.5;
     *    renderTexture.render(sprite);
     *
     * The Sprite in this case will be rendered to a position of 0,0. To render this sprite at its actual position a DisplayObjectContainer should be used:
     *
     *    var doc = new PIXI.DisplayObjectContainer();
     *    doc.addChild(sprite);
     *    renderTexture.render(doc);  // Renders to center of renderTexture
     *
     * @class RenderTexture
     * @extends Texture
     * @constructor
     * @param width {Number} The width of the render texture
     * @param height {Number} The height of the render texture
     * @param renderer {CanvasRenderer|WebGLRenderer} The renderer used for this RenderTexture
     * @param scaleMode {Number} See {{#crossLink "PIXI/scaleModes:property"}}PIXI.scaleModes{{/crossLink}} for possible values
     * @param resolution {Number} The resolution of the texture being generated
     */
    PIXI.RenderTexture = function(width, height, renderer, scaleMode, resolution)
    {
        /**
         * The with of the render texture
         *
         * @property width
         * @type Number
         */
        this.width = width || 100;

        /**
         * The height of the render texture
         *
         * @property height
         * @type Number
         */
        this.height = height || 100;

        /**
         * The Resolution of the texture.
         *
         * @property resolution
         * @type Number
         */
        this.resolution = resolution || 1;

        /**
         * The framing rectangle of the render texture
         *
         * @property frame
         * @type Rectangle
         */
        this.frame = new PIXI.Rectangle(0, 0, this.width * this.resolution, this.height * this.resolution);

        /**
         * This is the area of the BaseTexture image to actually copy to the Canvas / WebGL when rendering,
         * irrespective of the actual frame size or placement (which can be influenced by trimmed texture atlases)
         *
         * @property crop
         * @type Rectangle
         */
        this.crop = new PIXI.Rectangle(0, 0, this.width * this.resolution, this.height * this.resolution);

        /**
         * The base texture object that this texture uses
         *
         * @property baseTexture
         * @type BaseTexture
         */
        this.baseTexture = new PIXI.BaseTexture();
        this.baseTexture.width = this.width * this.resolution;
        this.baseTexture.height = this.height * this.resolution;
        this.baseTexture._glTextures = [];
        this.baseTexture.resolution = this.resolution;

        this.baseTexture.scaleMode = scaleMode || PIXI.scaleModes.DEFAULT;

        this.baseTexture.hasLoaded = true;

        PIXI.Texture.call(this,
            this.baseTexture,
            new PIXI.Rectangle(0, 0, this.width * this.resolution, this.height * this.resolution)
        );

        /**
         * The renderer this RenderTexture uses. A RenderTexture can only belong to one renderer at the moment if its webGL.
         *
         * @property renderer
         * @type CanvasRenderer|WebGLRenderer
         */
        this.renderer = renderer || PIXI.defaultRenderer;

        if (this.renderer.type === PIXI.WEBGL_RENDERER)
        {
            var gl = this.renderer.gl;
            this.baseTexture._dirty[gl.id] = false;

            this.textureBuffer = new PIXI.FilterTexture(gl, this.width, this.height, this.baseTexture.scaleMode);
            this.baseTexture._glTextures[gl.id] =  this.textureBuffer.texture;

            this.render = this.renderWebGL;
            this.projection = new PIXI.Point(this.width * 0.5, -this.height * 0.5);
        }
        else
        {
            this.render = this.renderCanvas;
            this.textureBuffer = new PIXI.CanvasBuffer(this.width * this.resolution, this.height * this.resolution);
            this.baseTexture.source = this.textureBuffer.canvas;
        }

        /**
         * @property valid
         * @type Boolean
         */
        this.valid = true;

        this.tempMatrix = new Phaser.Matrix();

        this._updateUvs();
    };

    PIXI.RenderTexture.prototype = Object.create(PIXI.Texture.prototype);
    PIXI.RenderTexture.prototype.constructor = PIXI.RenderTexture;

    /**
     * Resizes the RenderTexture.
     *
     * @method resize
     * @param width {Number} The width to resize to.
     * @param height {Number} The height to resize to.
     * @param updateBase {Boolean} Should the baseTexture.width and height values be resized as well?
     */
    PIXI.RenderTexture.prototype.resize = function(width, height, updateBase)
    {
        if (width === this.width && height === this.height)return;

        this.valid = (width > 0 && height > 0);

        this.width = width;
        this.height = height;
        this.frame.width = this.crop.width = width * this.resolution;
        this.frame.height = this.crop.height = height * this.resolution;

        if (updateBase)
        {
            this.baseTexture.width = this.width * this.resolution;
            this.baseTexture.height = this.height * this.resolution;
        }

        if (this.renderer.type === PIXI.WEBGL_RENDERER)
        {
            this.projection.x = this.width / 2;
            this.projection.y = -this.height / 2;
        }

        if(!this.valid)return;

        this.textureBuffer.resize(this.width, this.height);
    };

    /**
     * Clears the RenderTexture.
     *
     * @method clear
     */
    PIXI.RenderTexture.prototype.clear = function()
    {
        if (!this.valid)
        {
            return;
        }

        if (this.renderer.type === PIXI.WEBGL_RENDERER)
        {
            this.renderer.gl.bindFramebuffer(this.renderer.gl.FRAMEBUFFER, this.textureBuffer.frameBuffer);
        }

        this.textureBuffer.clear();
    };

    /**
     * This function will draw the display object to the texture.
     *
     * @method renderWebGL
     * @param displayObject {DisplayObject} The display object to render this texture on
     * @param [matrix] {Matrix} Optional matrix to apply to the display object before rendering.
     * @param [clear] {Boolean} If true the texture will be cleared before the displayObject is drawn
     * @private
     */
    PIXI.RenderTexture.prototype.renderWebGL = function(displayObject, matrix, clear)
    {
        if (!this.valid || displayObject.alpha === 0)
        {
            return;
        }

        //  Let's create a nice matrix to apply to our display object.
        //  Frame buffers come in upside down so we need to flip the matrix.
        var wt = displayObject.worldTransform;
        wt.identity();
        wt.translate(0, this.projection.y * 2);

        if (matrix)
        {
            wt.append(matrix);
        }

        wt.scale(1, -1);

        //  Time to update all the children of the displayObject with the new matrix.
        for (var i = 0; i < displayObject.children.length; i++)
        {
            displayObject.children[i].updateTransform();
        }

        //  Time for the webGL fun stuff!
        var gl = this.renderer.gl;

        gl.viewport(0, 0, this.width * this.resolution, this.height * this.resolution);

        gl.bindFramebuffer(gl.FRAMEBUFFER, this.textureBuffer.frameBuffer );

        if (clear)
        {
            this.textureBuffer.clear();
        }

        this.renderer.spriteBatch.dirty = true;

        this.renderer.renderDisplayObject(displayObject, this.projection, this.textureBuffer.frameBuffer, matrix);

        this.renderer.spriteBatch.dirty = true;

    };

    /**
     * This function will draw the display object to the texture.
     *
     * @method renderCanvas
     * @param displayObject {DisplayObject} The display object to render this texture on
     * @param [matrix] {Matrix} Optional matrix to apply to the display object before rendering.
     * @param [clear] {Boolean} If true the texture will be cleared before the displayObject is drawn
     * @private
     */
    PIXI.RenderTexture.prototype.renderCanvas = function(displayObject, matrix, clear)
    {
        if (!this.valid || displayObject.alpha === 0)
        {
            return;
        }

        //  Let's create a nice matrix to apply to our display object.
        //  Frame buffers come in upside down so we need to flip the matrix.
        var wt = displayObject.worldTransform;
        wt.identity();

        if (matrix)
        {
            wt.append(matrix);
        }

        // Time to update all the children of the displayObject with the new matrix (what new matrix? there isn't one!)
        for (var i = 0; i < displayObject.children.length; i++)
        {
            displayObject.children[i].updateTransform();
        }

        if (clear)
        {
            this.textureBuffer.clear();
        }

        var realResolution = this.renderer.resolution;

        this.renderer.resolution = this.resolution;

        this.renderer.renderDisplayObject(displayObject, this.textureBuffer.context, matrix);

        this.renderer.resolution = realResolution;
    };

    /**
     * Will return a HTML Image of the texture
     *
     * @method getImage
     * @return {Image}
     */
    PIXI.RenderTexture.prototype.getImage = function()
    {
        var image = new Image();
        image.src = this.getBase64();
        return image;
    };

    /**
     * Will return a base64 encoded string of this texture. It works by calling RenderTexture.getCanvas and then running toDataURL on that.
     *
     * @method getBase64
     * @return {String} A base64 encoded string of the texture.
     */
    PIXI.RenderTexture.prototype.getBase64 = function()
    {
        return this.getCanvas().toDataURL();
    };

    /**
     * Creates a Canvas element, renders this RenderTexture to it and then returns it.
     *
     * @method getCanvas
     * @return {HTMLCanvasElement} A Canvas element with the texture rendered on.
     */
    PIXI.RenderTexture.prototype.getCanvas = function()
    {
        if (this.renderer.type === PIXI.WEBGL_RENDERER)
        {
            var gl =  this.renderer.gl;
            var width = this.textureBuffer.width;
            var height = this.textureBuffer.height;

            var webGLPixels = new Uint8Array(4 * width * height);

            gl.bindFramebuffer(gl.FRAMEBUFFER, this.textureBuffer.frameBuffer);
            gl.readPixels(0, 0, width, height, gl.RGBA, gl.UNSIGNED_BYTE, webGLPixels);
            gl.bindFramebuffer(gl.FRAMEBUFFER, null);

            var tempCanvas = new PIXI.CanvasBuffer(width, height);
            var canvasData = tempCanvas.context.getImageData(0, 0, width, height);
            canvasData.data.set(webGLPixels);

            tempCanvas.context.putImageData(canvasData, 0, 0);

            return tempCanvas.canvas;
        }
        else
        {
            return this.textureBuffer.canvas;
        }
    };