Browser becomes unresponsive after running code to screenshot canvas.

I wrote some code to extract a screenshot from the canvas

function captureImage(filename, scale) {
    // Get the Verge3D application object.
    var app = document.v3dApp;

    // Get the renderer and scene from the application.
    var renderer = app.renderer;
    var scene = app.scene;
    var camera = app.camera;

    // save the old render target and autoClear state.
    var oldRenderTarget = renderer.getRenderTarget();
    var oldAutoClear = renderer.autoClear;

    var width = renderer.domElement.width * scale;
    var height = renderer.domElement.height * scale;

    // Increase the resolution of the WebGLRenderTarget and the canvas.
    var renderTargetWidth = width * window.devicePixelRatio;
    var renderTargetHeight = height * window.devicePixelRatio;

    var renderTarget = new document.v3d.WebGLRenderTarget(
        renderTargetWidth,
        renderTargetHeight,
        {
            minFilter: document.v3d.LinearFilter,
            magFilter: document.v3d.LinearFilter,
            format: document.v3d.RGBAFormat,
            stencilBuffer: false,
            depthBuffer: true
        }
    );

    // Disable autoClear before rendering to the new target.
    renderer.autoClear = false;

    // Render the scene to the WebGLRenderTarget.
    renderer.setRenderTarget(renderTarget);
    renderer.render(scene, camera);

    // Re-enable autoClear and restore the original render target.
    renderer.autoClear = oldAutoClear;
    renderer.setRenderTarget(oldRenderTarget);

    // Increase the resolution of the canvas.
    var canvas = document.createElement('canvas');
    canvas.width = renderTargetWidth;
    canvas.height = renderTargetHeight;
    var context = canvas.getContext('2d');

    var imageData = context.createImageData(canvas.width, canvas.height);

    renderer.readRenderTargetPixels(renderTarget, 0, 0, canvas.width, canvas.height, imageData.data);

    // Flip the image vertically by manipulating the imageData object.
    var flippedData = new Uint8ClampedArray(imageData.data.length);
    var stride = canvas.width * 4; // 4 bytes per pixel
    for (var y = 0; y < canvas.height; y++) {
        var sourceRow = y * stride;
        var targetRow = (canvas.height - y - 1) * stride;
        flippedData.set(imageData.data.subarray(sourceRow, sourceRow + stride), targetRow);
    }
    imageData.data.set(flippedData);

    context.putImageData(imageData, 0, 0);

    // Convert the rendered image to a data URL.
    var dataURL = canvas.toDataURL('image/png');

    // Use the data URL to create an HTML image element or download the image as a file.
    // For example, to download the image as a file:
    var link = document.createElement('a');
    link.href = dataURL;
    link.download = filename + '.png';
    link.click();
}

It works, and the 3d application continues to work, but only for a few seconds. After that, the program becomes unresponsive. I get no errors, but I assume it’s processing something and taking too much time.

I think it has something to do with changing the render target. Is there anything else I need to do to restore the application after running this code? Are there other ways to capture the image from the canvas?

Thanks,