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lib/image2json.js

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+/*
+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,
+    },
+  };
+}