write_picture/src/WriteImage.js

"Una librería de dibujo a mano libre sobre canvas con fondo de imagen.

export class WriteImage {
    constructor({ canvas, imageUrl, color, lineWidth }) {
        this.canvas = canvas;
        this.ctx = this.canvas.getContext('2d');
        this.imageUrl = imageUrl;
        this.drawing = false;
        this.color = color || '#ff0000';
        this.lineWidth = lineWidth || 5;
        
        // Cargar la imagen de fondo
        this.image = new Image();
        if (this.imageInput.startsWith('data:image')) {
            image.src = this.imageInput; // Es Base64
        } else {
            image.src = this.imageInput; // Es URL
        }
        
        this.addEventListeners();
    }

    
    startDrawing(e) {
        this.drawing = true;
        this.draw(e);
    }

    stopDrawing() {
        this.drawing = false;
        this.ctx.beginPath();
    }

    setSize(number) {
        this.lineWidth = number;
    }

    draw(e) {
        if (!this.drawing) return;

        const rect = this.canvas.getBoundingClientRect();
        const x = e.clientX - rect.left;
        const y = e.clientY - rect.top;

        this.ctx.lineWidth = this.lineWidth;
        this.ctx.lineCap = 'round';
        this.ctx.strokeStyle = this.color;

        this.ctx.lineTo(x, y);
        this.ctx.stroke();
        this.ctx.beginPath();
        this.ctx.moveTo(x, y);
    }

    // Método para cambiar el color del lápiz
    setColor(newColor) {
        this.color = newColor;
    }

    // Método para borrar los dibujos, pero manteniendo la imagen de fondo
    clearCanvas() {
        this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height);
        this.ctx.drawImage(this.image, 0, 0, this.canvas.width, this.canvas.height);
    }

    // Método para descargar la imagen con los dibujos
    getImage() {
        return this.canvas.toDataURL('image/png');
    }

    // Agregar los event listeners
    addEventListeners() {
        // Evento para dibujar
        this.canvas.addEventListener('mousedown', (e) => this.startDrawing(e));
        this.canvas.addEventListener('mouseup', () => this.stopDrawing());
        this.canvas.addEventListener('mousemove', (e) => this.draw(e));
    }
}