figura-tools/lib/image2json.js

/*
MIT License

Copyright (c) 2024 Sol Toder

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

Copy available at https://github.com/AjaxGb/mc-text-image/blob/master/LICENSE
*/

import * as fs from "fs";

import { createCanvas, loadImage } from "@napi-rs/canvas";

const BLOCK_CHAR = "\u2587";
const SPACE_CHAR = "\u2007";
const TRAILING_SPACE = new RegExp(SPACE_CHAR + "+$");
const FONT_RATIO = 1.8;

function parseSize(text) {
  const parsed = parseInt(text);
  return parsed > 0 ? parsed : 0;
}

function calcSize(origW, origH, width, height, keepRatio, pixelShape) {
  let w = width || origW;
  let h = height || origH;

  if (keepRatio) {
    const originRatio = origW / origH;
    const currRatio = w / h;

    if (currRatio > originRatio || (origH && !origW)) {
      w = (h * origW) / origH;
    } else {
      h = (w * origH) / origW;
    }
  }

  const pixelRatio = pixelShape === "font" ? FONT_RATIO : 1.0;

  return {
    w: Math.round(w),
    h: Math.round(h / pixelRatio),
    unscaledH: Math.round(h),
    origW,
    origH,
  };
}

function hexNibble(value) {
  return value.toString(16).padStart(2, "0");
}

function makeHexColor(pixels, offset, cutoff) {
  const a = pixels[offset + 3];
  if (a < cutoff) {
    pixels[offset + 3] = 0;
    return null;
  } else {
    pixels[offset + 3] = 255;
    const r = pixels[offset + 0];
    const g = pixels[offset + 1];
    const b = pixels[offset + 2];
    return "#" + hexNibble(r) + hexNibble(g) + hexNibble(b);
  }
}
export async function imageToJson(imageBuffer, options = {}) {
  const {
    width = null,
    height = null,
    keepRatio = true,
    pixelShape = "square",
    smoothing = null,
    transparencyCutoff = 0,
    stripSpace = false,
  } = options;

  if (!imageBuffer || !(imageBuffer instanceof Uint8Array)) {
    console.error("imageToJson: Invalid imageBuffer provided.");
    throw new Error(`Input must be a Buffer containing image data`);
  }

  let image;
  try {
    image = await loadImage(imageBuffer);
  } catch (err) {
    console.error("imageToJson: Failed to load image from buffer.", err);
    throw err;
  }
  if (!image || !image.width || !image.height) {
    console.error(
      "imageToJson: Loaded image is invalid or missing dimensions.",
    );
    throw new Error("Loaded image is invalid or missing dimensions.");
  }
  const origW = image.width;
  const origH = image.height;

  let sizeObj;
  try {
    sizeObj = calcSize(origW, origH, width, height, keepRatio, pixelShape);
  } catch (err) {
    console.error("imageToJson: Failed to calculate target size.", err);
    throw err;
  }
  const { w, h } = sizeObj;

  let canvas, ctx;
  try {
    canvas = createCanvas(w, h);
    ctx = canvas.getContext("2d");
  } catch (err) {
    console.error("imageToJson: Failed to create canvas or context.", err);
    throw err;
  }

  try {
    if (smoothing) {
      ctx.imageSmoothingEnabled = true;
      ctx.imageSmoothingQuality = smoothing;
    } else {
      ctx.imageSmoothingEnabled = false;
    }
  } catch (err) {
    console.error("imageToJson: Failed to set image smoothing.", err);
    throw err;
  }

  try {
    ctx.clearRect(0, 0, w, h);
    ctx.drawImage(image, 0, 0, w, h);
  } catch (err) {
    console.error("imageToJson: Failed to draw image on canvas.", err);
    throw err;
  }

  let cutoff, imageData, pixels;
  try {
    cutoff = parseInt(transparencyCutoff) || 0;
    imageData = ctx.getImageData(0, 0, w, h);
    pixels = imageData.data;
  } catch (err) {
    console.error("imageToJson: Failed to get image data from canvas.", err);
    throw err;
  }
  const json = [];
  let currColor = null;
  let currText = "";

  const totalPixels = pixels.length / 4;

  for (let x = 0, i = 0; i < pixels.length; x++, i += 4) {
    if (x >= w) {
      if (stripSpace) {
        currText = currText.replace(TRAILING_SPACE, "");
      }
      currText += "\n";
      x = 0;
    }

    let newColor;
    try {
      newColor = makeHexColor(pixels, i, cutoff);
    } catch (err) {
      console.error(`imageToJson: Error processing pixel at index ${i}.`, err);
      throw err;
    }
    if (currColor && newColor && currColor != newColor) {
      json.push({ text: currText, color: currColor });
      currText = "";
    }

    if (newColor) {
      currColor = newColor;
      currText += BLOCK_CHAR;
    } else {
      currText += SPACE_CHAR;
    }
  }

  if (stripSpace) {
    currText = currText.replace(TRAILING_SPACE, "");
  }

  if (currText && currColor) {
    json.push({ text: currText, color: currColor });
  }

  return {
    json: json,
    dimensions: {
      width: w,
      height: h,
      originalWidth: origW,
      originalHeight: origH,
    },
  };
}