The start and end points of the image

Question

I'm trying to set the start and end points of an image. So I have my canvas and an image and when I put the image into the canvas I want it to light up a little red circle when I hover over the start/end points which means I can create with other images connect. For example: 1) Drag the image. 2) Place the image into the canvas. 3) Hover the mouse to the starting point/end point, and the little red dot will light up. As you can see, the red dot only appears on hover. Another question, but cool if you solve the first one, the image doesn't follow the grill (square). This is an example constresistor for html/js

P粉214089349 · Answer

You can keep track of the x and y of the image in the array and iterate over the array to check if the mouse pointer is some distance away from any object, if so then draw a circle and in the remote image the connection is if you plan to add more than 2 The image shown (don't know about locally hosted images) and the start and end points are different, then at the midpoint of both sides you will need to use the current settings based on the image change value, you can hardcode it, here is mine accomplish:

const resistor = document.getElementById('component_circuit_resistor');
const condensator = document.getElementById('component_circuit_condensator');
const tranistor = document.getElementById('component_circuit_tranistor');
const alimentator = document.getElementById('component_circuit_alimentator');
const circuit = document.getElementById('components_circuit');
const back_button = document.getElementById('back-button');
const clear_button = document.getElementById('clear-button');
const draggable = document.querySelectorAll('.draggable');
const container = document.querySelectorAll('.container');
const canvas = document.getElementById('canvas');
const foward_button = document.getElementById('foward-button');
let images = [];

/** EDIT START */
const draggableImages = document.querySelectorAll('img[draggable]');

for (let i = 0; i < draggableImages.length; i++)
  draggableImages[i].ondragstart = (ev) => {
    ev.dataTransfer.setData('text/plain', i.toString());
  };

canvas.ondragover = (ev) => ev.preventDefault(); // IMPORTANT

const orderStack = [];
const deletedOrderStack = [];

const drawnImageData = [];
const deletedImageData = [];
canvas.ondrop = (ev) => {
    
    const index = parseInt(ev.dataTransfer.getData('text/plain'));
    const img = draggableImages[index];
    const x = ev.clientX - canvas.offsetLeft - img.width / 2;
    const y = ev.clientY - canvas.offsetTop - img.height / 2;
    const squareSize = 10; // adjust this to match the size of your squares


    const maxSize = 75; // maximum size of the image
    const aspectRatio = img.width / img.height;
    let width = maxSize;
    let height = maxSize / aspectRatio;
    if (height > maxSize) {
      height = maxSize;
      width = height * aspectRatio;
    }
    const snappedX = Math.round(x / squareSize) * squareSize;
    const snappedY = Math.round(y / squareSize) * squareSize;
    ctx.drawImage(img, snappedX, snappedY, width, height);
    images.push({ img, x: snappedX, y: snappedY, width, height });
    // Add the image and its position to the images array

  };
  

  
 
clear_button.disabled = true;
clear_button.style.cursor = 'not-allowed';
foward_button.disabled = true;
foward_button.style.cursor = 'not-allowed';
back_button.disabled = true;
back_button.style.cursor = 'not-allowed';
/** EDIT END */

canvas.width = 1900;

canvas.height = 1000;
canvas.style.backgroundColor = 'white';
circuit.appendChild(canvas);
canvas.style.borderRadius = '10px';
canvas.style.marginLeft = 'auto';
canvas.style.marginRight = 'auto';
canvas.style.display = 'block';
const ctx = canvas.getContext('2d');

//const circles = [];
const lines = [];
const lines_c = [];
var deletedLines = [];

function drawSquares() {
  const squareSize = 10;
  const numColumns = Math.floor(canvas.width / squareSize);
  const numRows = Math.floor(canvas.height / squareSize);

  ctx.fillStyle = "#FAF9F9";
  ctx.strokeStyle = "#F4F1F0";
  ctx.lineWidth = 1;

  for (let i = 0; i < numColumns; i++) {
    for (let j = 0; j < numRows; j++) {
      const x = i * squareSize;
      const y = j * squareSize;

      if (i % 10 === 0 && j % 10 === 0) {
        ctx.lineWidth = 2.6;
        ctx.fillStyle = "#F1ECEB";
        ctx.strokeStyle = "#E6E0DE"; // set the stroke color to a darker shade
        ctx.strokeRect(x, y, squareSize * 10, squareSize * 10);
        ctx.fillStyle = "#F4F1F0";
        ctx.strokeStyle = "#F4F1F0"; // reset the stroke color
        ctx.lineWidth = 1;
      } else {
        ctx.strokeRect(x, y, squareSize, squareSize);
      }
    }
  }
}

drawSquares();

// Add a mousemove event to the canvas to show the red dot
  const redDotRadius = 5; // The radius of the red dots
  const hoverDistance = 10; // The distance from a point at which to show the dot

canvas.onmousemove = (ev) => {
    const mouseX = ev.clientX - canvas.offsetLeft;
    const mouseY = ev.clientY - canvas.offsetTop;
    
    // Clear the canvas and redraw everything
    ctx.clearRect(0, 0, canvas.width, canvas.height);
    drawSquares();
    for (let i = 0; i < images.length; i++) {
      let image = images[i];
      ctx.drawImage(image.img, image.x, image.y, image.width, image.height);
    }
    
    // Check if the mouse is near a starting or ending point
    for (let i = 0; i < images.length; i++) {
      let image = images[i];
      let startX = image.x+5;
      let startY = image.y + image.height/2;
      let endX = image.x + image.width -5;
      let endY = image.y + image.height/2;
      
      if (Math.abs(mouseX - startX) < hoverDistance && Math.abs(mouseY - startY) < hoverDistance) {
        // Near the starting point, draw a red dot
        ctx.beginPath();
        ctx.arc(startX, startY, redDotRadius, 0, 2 * Math.PI, false);
        ctx.fillStyle = 'red';
        ctx.fill();
      } else if (Math.abs(mouseX - endX) < hoverDistance && Math.abs(mouseY - endY) < hoverDistance) {
        // Near the ending point, draw a red dot
        ctx.beginPath();
        ctx.arc(endX, endY, redDotRadius, 0, 2 * Math.PI, false);
        ctx.fillStyle = 'red';
        ctx.fill();
      }
    }
  };

I didn’t change the html

The start and end points of the image

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