How to crop an image with canvas and Kinetic.js

问题:

my function draw an image, and another image on another layer with Kinetic.js but i want to crop the second image which is named smsTopBg_image

    window.onload = function() {
        //INITIALISATION
        var stage = new Kinetic.Stage({
            container: "iPhone",
            width: 480,
            height: 720
        });
        //LAYERS
        var background_layer = new Kinetic.Layer();
        var sms_layer = new Kinetic.Layer();
        var text_layer = new Kinetic.Layer();

        //ELEMENTS
        var iPhoneBg = new Image();
        iPhoneBg.onload = function() {
                var iPhoneBg_image = new Kinetic.Image({
                image: iPhoneBg
            });
            background_layer.add(iPhoneBg_image);
            stage.add(background_layer);
        }
        iPhoneBg.src = "iPhoneBg.jpg";
        //--------------------------------------------------
        var smsTopBg = new Image();
            smsTopBg.onload = function() {
                var smsTopBg_image = new Kinetic.Image({
                image: smsTopBg,
                x: 10,
                y: 10,
            });
            sms_layer.add(smsTopBg_image);
            stage.add(sms_layer);
        }
        smsTopBg.src = "iPhoneBg.jpg";
    };

Thanks !

回答1:

You can add an optional crop object to the main attributes object in your Image constructor. It has an x, y, width and height properties.

var smsTopBg_image = new Kinetic.Image({
    image: smsTopBg,
    x: 10,
    y: 10,
    // random values, choose your own :
    crop: {
        x: 20,
        y: 3,
        width: 100,
        height: 42
    }
});

回答2:

Ok ifound the complete solution with your help, it's necessary to add height and with to the image before crop like that :

var smsTopBg = new Image();
            smsTopBg.onload = function() {
                var smsTopBg_image = new Kinetic.Image({
                image: smsTopBg,
                x: 200,
                y: 20,
                    width: 50,
                    height: 20,
                crop: {
                    x: 20,
                    y: 10,
                    width: 50,
                    height: 50
                }

            });
            sms_layer.add(smsTopBg_image);
            stage.add(sms_layer);
        }

Thanks !

回答3:

Refer this url for Image Crop in Kinetic.js : http://jsfiddle.net/umhm7/