//      this.capture()
       //     this.captureAndShow()
        //    this.saveFile('ttt')
       
    capture () {
        let camera = this.camera = cc.find('Canvas/Camera').getComponent(cc.Camera);
    
        // 设置你想要的截图内容的 cullingMask
        camera.cullingMask = 0xffffffff;
    
        // 新建一个 RenderTexture，并且设置 camera 的 targetTexture 为新建的 RenderTexture，这样        camera 的内容将会渲染到新建的 RenderTexture 中。
        let texture = new cc.RenderTexture();
        this.texture = texture ;
        let gl = cc.game._renderContext;
    
        // 如果截图内容中不包含 Mask 组件，可以不用传递第三个参数
        texture.initWithSize(cc.visibleRect.width, cc.visibleRect.height, gl.STENCIL_INDEX8);
        camera.targetTexture = texture;
    
        let width = this.texture.width;
        let height = this.texture.height;
        if (!this.canvas) {
            this.canvas = document.createElement('canvas');

            this.canvas.width = width;
            this.canvas.height = height;
        }
        let ctx = this.canvas.getContext('2d');
        this.camera.render();
        let data = this.texture.readPixels();
        // write the render data
        let rowBytes = width * 4; 
        for (let row = 0; row < height; row++) {
            let srow = height - 1 - row;
            let imageData = ctx.createImageData(width, 1);
            let start = srow * width * 4;
            for (let i = 0; i < rowBytes; i++) {
                imageData.data[i] = data[start + i];
            }

            ctx.putImageData(imageData, 0, row);
        }

        var dataURL = this.canvas.toDataURL("image/jpeg");
        var img = document.createElement("img");
        img.src = dataURL;
        return img;

    }, 
 
    //需要显示时 调用此方法
    captureAndShow () {
        var img = this.capture();
 
        // You can save the image or show it.
 
        // img.style.position = 'absolute';
        // img.style.display = 'block';
        // img.style.left = '0px'
        // img.style.top = '0px';
        // img.zIndex = 100;
 
        // img.style.transform = cc.game.container.style.transform;
        // img.style['transform-origin'] = cc.game.container.style['transform-origin'];
        // img.style.margin = cc.game.container.style.margin;
        // img.style.padding = cc.game.container.style.padding;
 
        // img.onclick = function (event) {
        //     event.stopPropagation();
        //     img.remove();
        // }
 
        // document.body.appendChild(img);
 
        let texture = new cc.Texture2D();
        texture.initWithElement(img);
 
        let spriteFrame = new cc.SpriteFrame();
        spriteFrame.setTexture(texture);
 
        let node = new cc.Node();
        node.parent = cc.director.getScene();
        node.zIndex = cc.macro.MAX_ZINDEX;
 
        let sprite = node.addComponent(cc.Sprite);
        sprite.spriteFrame = spriteFrame;
        
        node.x = cc.winSize.width/2;
        node.y = cc.winSize.height/2;
        node.scaleX = 1/2
        node.scaleY = 1/2
        //测试用 点击销毁图片
        node.on(cc.Node.EventType.TOUCH_START, () => {
            node.destroy();
        });
    },

    saveFile ( fileName){
        //保存的方法前端有很多,这里暂时用这个
        
        let data =this.canvas.toDataURL("image/png");
        let save_link = document.createElement('a');
        save_link.href = data;
        save_link.download = fileName;
 
        let event = document.createEvent('MouseEvents');
        event.initEvent("click", true, false);
        save_link.dispatchEvent(event);
    },

原文 https://blog.csdn.net/qq_20173207/article/details/85522653
https://blog.csdn.net/yzx5452830/article/details/83446310
https://github.com/Leo501/CocosCreatorTutorial/blob/master/Screenshot/assets/Script/Screenshot.js
如果截图后背景是黑色的可以参考下面把camera设置background为(0,0,0,0)
https://www.jianshu.com/p/e5a8ffb0fd77
去掉背景，截取某一个node的test

captureToNode () {
        var node = this.node
        var my = node.getChildByName('my')
        var bg = my.getChildByName("bg")
        var mmm = my.getChildByName("mmm")

        var size = cc.winSize
        cc.log(size) 

        var mmmSize = cc.size(mmm.width*mmm.scaleX, mmm.height*mmm.scaleY)
       mmmSize.x = mmm.x - mmm.width*mmm.anchorX*mmm.scaleX
        mmmSize.y = mmm.y - mmm.height*mmm.anchorY*mmm.scaleY
        cc.log(mmmSize) 

        bg.active = false
        var img = util.capture()
        bg.active = true

        var texture = new cc.Texture2D();
        texture.initWithElement(img);

        var spriteFrame = new cc.SpriteFrame();
        spriteFrame.setTexture(texture);
        spriteFrame.setRect(cc.rect(mmmSize.x,size.height - mmmSize.y - mmmSize.height,mmmSize.width,mmmSize.height));

        var node = new cc.Node();
        var sprite = node.addComponent(cc.Sprite);
        sprite.spriteFrame = spriteFrame;

        return node
    },

var node = this.captureToNode()
     node.parent = cc.director.getScene();
     node.zIndex = cc.macro.MAX_ZINDEX;
     node.setAnchorPoint(0, 0); 
     node.setScale(2, 2);