I have photos distributed as cells. When I click, I get the corresponding row and column.
console.log("Col:" + X + "Row:" + Y);
When applying an isometric view conversion like this:
ctx.translate(0, 300);
ctx.scale(1, 0.5);
ctx.rotate(-45 * Math.PI /180);
I do not know what mathematical formula applies to get the coordinates correctly.

Based on feedback so far, I've been able to get this far. The x coordinate seems to work fine, but the y coordinate not.
Isometrico();
function Isometrico(){
ctx.translate(0, 300);
ctx.scale(1, 0.5);
var radianes= -45 * Math.PI /180;
ctx.rotate(radianes);
}
/*
document.addEventListener("mousedown", function(e) {
CorIsometrico( e.offsetX, e.offsetY);
});
*/
/*
function CorIsometrico(xI,yI){
//RESPUESTA yI=yI-300;
yI = yI * 2;
xI = xI * Math.cos(45) - yI * Math.sin(45);
I = yI * Math.sin(45) + yI * Math.cos(45);
console.log("Coor Isometricas:" + xI + "/"+ + yI);
}
*/
Edit:
Each cell is 50x50. Having 10 columns and 50 rows, the information of each cell would look like this:
1: 50/50
2: 100/50
3: 150/50
...
49: 450/250
50: 500/250
Maximum Y value = 250.
xI=xIMath.cos(45 / 180 * Math.PI)-yIMath.sin(45 / 180 * Math.PI);
yI=yIMath.sin(45 / 180 * Math.PI)+yIMath.cos(45 / 180 * Math.PI);
yI=yI*2;
yI=yI-300;
Click in X:1 / Y:1 = -138.5929291125633/ 531.5575746753798
Click in X:1 / Y:5= 198.69700551341987/ 90.3229432149742
Y exceeds the maximum value.