Utilizing getImageData and putImageData in the Canvas Puzzle Project

Below is the code I've written to interact with my canvas:

function clickBox() //Function to retrieve cell coordinates on the grid.
{
    var xRectFill = 0; 
    var yRectFill = 0; 
    var rectFillArrayX = [];
    var rectFillArrayY = [];
    var mouseX = event.offsetX;
    var mouseY = event.offsetY;
    for (i3 = 0; i3 <= 8; i3++) 
    {
        rectFillArrayX[i3] = xRectFill; 
        rectFillArrayY[i3] = yRectFill; 
        xRectFill += 72; 
        yRectFill += 72; 
    }
    for (i4 = 0; i4 <= 8; i4++)
    {
        if (mouseX >= rectFillArrayX[i4] && mouseX <= (rectFillArrayX[i4] + 72))
        {
            for (i5 = 0; i5 <= 8; i5++)
            {
                if (mouseY >= rectFillArrayY[i5] && mouseY <= (rectFillArrayY[i5] + 72))
                {
                    ctx.clearRect(rectFillArrayX[i4], rectFillArrayY[i5], 71, 71);
                }
            }
        }
    }
}

I'm currently working on a sudoku puzzle design using a 9x9 grid. The "clickBox" function successfully retrieves mouse coordinates and clears cells upon a click event.

Now, I aim to duplicate the cleared portion of the canvas and reintegrate it whenever another area is clicked.

I've explored various techniques but failed to implement the getImageData and putImageData functions effectively.

One approach I tried involved storing X and Y coordinates when a box is cleared, then passing them to getImageData and placing putImageData during subsequent clicks. Unfortunately, this didn't yield the desired results.

The idea behind using getImageData before clearRect was to utilize the putImageData method on the previously cleared cell upon the next click.

If someone could demonstrate the proper usage of getImageData and putImageData in this scenario, that would be greatly appreciated.

Here's an attempt at solving the issue:

function clickBox() //Get every cell by coordinate on the grid.
{
    var xRectFill = 0; 
    var yRectFill = 0; 
    var rectFillArrayX = []; 
    var rectFillArrayY = []; 
    var mouseX = event.offsetX;
    var mouseY = event.offsetY;

    if (lastLocation[0] != null)
    {
        ctx.putImageData(imgData, lastLocation[0], lastLocation[1], 70);
    }
    for (i3 = 0; i3 <= 8; i3++) 
    {
        rectFillArrayX[i3] = xRectFill; 
        rectFillArrayY[i3] = yRectFill; 
        xRectFill += 72; 
        yRectFill += 72; 
    }
    for (i4 = 0; i4 <= 8; i4++)
    {
        if (mouseX >= rectFillArrayX[i4] && mouseX <= (rectFillArrayX[i4] + 72))
        {
            for (i5 = 0; i5 <= 8; i5++)
            {
                if (mouseY >= rectFillArrayY[i5] && mouseY <= (rectFillArrayY[i5] + 72))
                {
                    var imgData = ctx.getImageData(rectFillArrayX[i4], rectFillArrayY[i4], 72, 72);
                    var lastLocation = [rectFillArrayX[i4], rectFillArrayY[i5]];
                    ctx.clearRect(rectFillArrayX[i4], rectFillArrayY[i5], 71, 71);
                }
            }
        }
    }
}

Another attempt included:

function clickBox() //Get every cell by coordinate on the grid.
{
    var xRectFill = 0; 
    var yRectFill = 0; 
    var rectFillArrayX = []; 
    var rectFillArrayY = []; 
    var mouseX = event.offsetX;
    var mouseY = event.offsetY;
    var lastLocation = [];

    if (typeof lastLocation[0] !== 'undefined')
    {
        alert("Array is defined");
        ctx.putImageData(imgData, lastLocation[0], lastLocation[1], 70);
    }
    for (i3 = 0; i3 <= 8; i3++) 
    {
        rectFillArrayX[i3] = xRectFill; 
        rectFillArrayY[i3] = yRectFill; 
        xRectFill += 72; 
        yRectFill += 72; 
    }
    for (i4 = 0; i4 <= 8; i4++)
    {
        if (mouseX >= rectFillArrayX[i4] && mouseX <= (rectFillArrayX[i4] + 72))
        {
            for (i5 = 0; i5 <= 8; i5++)
            {
                if (mouseY >= rectFillArrayY[i5] && mouseY <= (rectFillArrayY[i5] + 72))
                {
                    var imgData = ctx.getImageData(rectFillArrayX[i4], rectFillArrayY[i4], 72, 72);
                    var lastLocation = [rectFillArrayX[i4], rectFillArrayY[i5]];
                    ctx.clearRect(rectFillArrayX[i4], rectFillArrayY[i5], 71, 71);
                }
            }
        }
    }
}

Check out the Puzzle Image Here

Answer №1

I successfully resolved the issue.

function clickBox() //Obtains every cell by coordinate on the grid.
{
    var xRectFill = 0; //Initiating search from the left side of the board.
    var yRectFill = 0; //Starting search from the top of the board.
    var rectFillArrayX = []; //Storing X-Coordinates of cells here.
    var rectFillArrayY = []; //Storing Y-Coordinates of cells here.
    var mouseX = event.offsetX;
    var mouseY = event.offsetY;
    if (typeof lastLocation !== 'undefined' && lastLocation.length > 0)
    {
        // Checking if array is defined and has elements
        ctx.putImageData(imgData, lastLocation[0], lastLocation[1]);
    }
    for (i3 = 0; i3 <= 8; i3++) //Filling the X and Y values in storage array.
    {
        rectFillArrayX[i3] = xRectFill; //Storing each X-Coordinate from [0-8]
        rectFillArrayY[i3] = yRectFill; //Storing each Y-Coordinate from [0-8]
        xRectFill += 72; //Getting next X value after filling one.
        yRectFill += 72; //Getting next Y value after filling one.
    }
    for (i4 = 0; i4 <= 8; i4++)
    {
        if (mouseX >= rectFillArrayX[i4] && mouseX <= (rectFillArrayX[i4] + 72))
        {
            for (i5 = 0; i5 <= 8; i5++)
            {
                if (mouseY >= rectFillArrayY[i5] && mouseY <= (rectFillArrayY[i5] + 72))
                {
                    lastLocation = [rectFillArrayX[i4], rectFillArrayY[i5]];
                    ctx.clearRect(rectFillArrayX[i4], rectFillArrayY[i5], 71, 71);
                }
            }
        }
    }
}

In another part of the code, I defined a global variable getImageData and included a check at the beginning to see if the array was created instead of creating an empty array beforehand.

Final additions:

if (typeof lastLocation !== 'undefined' && lastLocation.length > 0)
        {
            // array exists with at least one element
            ctx.putImageData(imgData, lastLocation[0], lastLocation[1]);
        }

Answer №2

To handle this, consider creating a table with each portion as a separate cell. This way, you can easily toggle the visibility of individual cells based on events or other triggers.

For example, you can initially hide a cell using

<tr id="your_cell" style="display: none;">
and then use JavaScript to display it again:

var cellWithData = document.getElementById('your_cell').style;
cellWithData.display = 'table-row'/'block'; 

If needed, cells can also be deleted dynamically:

var row = document.getElementById("myRow");
row.deleteCell(0);

This is just a suggestion for your consideration.

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