react-paint-test/src/util/snapshot/index.ts

a simple paint tool

/**
 * 使用两个栈实现canvas前进后退动作
 */
class Snapshot {
    private imageData1: ImageData[] = [];
    private imageData2: ImageData[] = [];
    public add(imageData: ImageData) {
        this.imageData1.push(imageData);
    }
    public get current() {
        return this.imageData1[this.imageData1.length - 1];
    }
    public back() {
        if (this.imageData1.length > 1) {
            const imageData = this.imageData1.pop() as ImageData;
            this.imageData2.push(imageData);
        }
        
        return this.imageData1.length > 0 ? this.imageData1[this.imageData1.length - 1] : null;
    }

    public forward() {
        if (this.imageData2.length > 0) {
            const imageData = this.imageData2.pop() as ImageData;
            this.imageData1.push(imageData);
        }
        return this.imageData1.length > 0 ? this.imageData1[this.imageData1.length - 1] : null;
    }
}

export default Snapshot;