Function composite

packages/core/src/utils/composite.ts:7–85

(
  baseImage: I,
  src: I,
  x = 0,
  y = 0,
  options: {
    mode?: BlendMode;
    opacitySource?: number;
    opacityDest?: number;
  } = {}
)

import { limit255 } from "@jimp/utils";

export function composite<I extends JimpClass>(
  baseImage: I,
  src: I,
  x = 0,
  y = 0,
  options: {
    mode?: BlendMode;
    opacitySource?: number;
    opacityDest?: number;
  } = {}
) {
  if (!(src instanceof baseImage.constructor)) {
    throw new Error("The source must be a Jimp image");
  }

  if (typeof x !== "number" || typeof y !== "number") {
    throw new Error("x and y must be numbers");
  }

  const { mode = BlendMode.SRC_OVER } = options;
  let { opacitySource = 1.0, opacityDest = 1.0 } = options;

  if (
    typeof opacitySource !== "number" ||
    opacitySource < 0 ||
    opacitySource > 1
  ) {
    opacitySource = 1.0;
  }

  if (typeof opacityDest !== "number" || opacityDest < 0 || opacityDest > 1) {
    opacityDest = 1.0;
  }

  const blendmode = compositeModes[mode];

  // round input
  x = Math.round(x);
  y = Math.round(y);

  if (opacityDest !== 1.0) {
    baseImage.scan((_, __, idx) => {
      const v = baseImage.bitmap.data[idx + 3]! * opacityDest;
      baseImage.bitmap.data[idx + 3] = v;
    });
  }

  src.scan((sx, sy, idx) => {
    const dstIdx = baseImage.getPixelIndex(x + sx, y + sy, Edge.CROP);

    if (dstIdx === -1) {
      // Skip target pixels outside of dst
      return;
    }

    const blended = blendmode(
      {
        r: src.bitmap.data[idx + 0]! / 255,