MediaWiki:CardToImage.js

/* jshint esversion: 10 */
/**
 * Convert a base64 string in a Blob according to the data and contentType.
 *
 * @param b64Data {String} Pure base64 string without contentType
 * @param contentType {String} the content type of the file i.e (image/jpeg - image/png - text/plain)
 * @param sliceSize {Int} SliceSize to process the byteCharacters
 * @see https://stackoverflow.com/questions/16245767
 * @return Blob
 */
function cardToImage() {
  function b64toBlob(b64Data, contentType = '', sliceSize = 512) {
    const byteCharacters = atob(b64Data);
    const byteArrays = [];

    for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {
      const slice = byteCharacters.slice(offset, offset + sliceSize);

      const byteNumbers = new Array(slice.length);
      for (let i = 0; i < slice.length; i++) {
        byteNumbers[i] = slice.charCodeAt(i);
      }

      const byteArray = new Uint8Array(byteNumbers);

      byteArrays.push(byteArray);
    }

    const blob = new Blob(byteArrays, { type: contentType });
    return blob;
  }

  // Generate screenshot and download
  const opt = {
    scrollX: -window.scrollX,
    scrollY: -window.scrollY,
  };
  const element = document.getElementById('cardCatalog');
  html2canvas(element, opt).then(function (canvas) {
    // Generate the base64 representation of the canvas
    const base64image = canvas.toDataURL('image/png');

    // Split the base64 string in data and contentType
    const block = base64image.split(';');
    // Get the content type
    const mimeType = block[0].split(':')[1]; // In this case "image/png"
    // get the real base64 content of the file
    const realData = block[1].split(',')[1]; // For example:  iVBORw0KGgouqw23....

    // Convert b64 to blob and store it into a variable (with real base64 as value)
    const canvasBlob = b64toBlob(realData, mimeType);

    // Generate file download
    window.saveAs(canvasBlob, 'Ficha.png');
  });
}