Function advancedRotate

plugins/plugin-rotate/src/index.ts:118–215

* Rotates an image counter-clockwise by an arbitrary number of degrees. NB: 'this' must be a Jimp object. * @param {number} deg the number of degrees to rotate the image by

(
  image: I,
  deg: number,
  mode: boolean | ResizeStrategy
)

 * @param {number} deg the number of degrees to rotate the image by
 */
function advancedRotate<I extends JimpClass>(
  image: I,
  deg: number,
  mode: boolean | ResizeStrategy
) {
  const rad = (deg * Math.PI) / 180;
  const cosine = Math.cos(rad);
  const sine = Math.sin(rad);

  // the final width and height will change if resize == true
  let w = image.bitmap.width;
  let h = image.bitmap.height;

  if (mode === true || typeof mode === "string") {
    // resize the image to it maximum dimension and blit the existing image
    // onto the center so that when it is rotated the image is kept in bounds

    // http://stackoverflow.com/questions/3231176/how-to-get-size-of-a-rotated-rectangle
    // Plus 1 border pixel to ensure to show all rotated result for some cases.
    w =
      Math.ceil(
        Math.abs(image.bitmap.width * cosine) +
          Math.abs(image.bitmap.height * sine)
      ) + 1;
    h =
      Math.ceil(
        Math.abs(image.bitmap.width * sine) +
          Math.abs(image.bitmap.height * cosine)
      ) + 1;
    // Ensure destination to have even size to a better result.
    if (w % 2 !== 0) {
      w++;
    }

    if (h % 2 !== 0) {
      h++;
    }

    const c = clone(image);

    image.scan((_, __, idx) => {
      image.bitmap.data.writeUInt32BE(image.background, idx);
    });

    const max = Math.max(w, h, image.bitmap.width, image.bitmap.height);
    image = resizeMethods.resize(image, {
      h: max,
      w: max,
      mode: mode === true ? undefined : mode,
    });

    image = composite(
      image,
      c,
      image.bitmap.width / 2 - c.bitmap.width / 2,
      image.bitmap.height / 2 - c.bitmap.height / 2
    );
  }