refactor ascii image conversio

Author: darcros

src/commands/context/ascii-image.mjs

@@ -39,8 +39,6 @@ export const execute = async (interaction) => {
 
   const result = await urlToAscii(
     attachment.proxyURL,
-    attachment.width,
-    attachment.height,
     // 2000 is the maximus size allowd by discord
     // -6 is to make space for the ``` before and after the message
     2000 - 6

src/util/imageToAscii.mjs

@@ -1,97 +1,70 @@
-import { pipeline } from 'stream/promises';
 import got from 'got';
 import sharp from 'sharp';
-import { PassThrough } from 'stream';
 
 // TODO: expand the caracter list
 const chars = '%&#MHGw*+-. ';
 // const chars = 'BS#&@$%*!:. ';
 
 /**
- * Calculate the maximum rectangle that has a surface area <= `maxSurface` and the same aspect ratio
- *
  * @param {number} width the image width
  * @param {number} height the image heigth
- * @param {number} maxSurface maximum surface area of the output rectangle
+ * @param {number} maxChars maximum character to use for the ASCII image
  * @returns
  */
-const calculateSize = (width, height, maxSurface = 2000) => {
+const calculateSize = (width, height, maxChars = 2000) => {
   const imageArea = width * height;
 
   /*
   We want to keep the aspect ratio of the image, this means that we must scale width and height by the same factor:
   (1) newW = scaleFactor * width
   (2) newH = scaleFactor * height
 
-  We also want the are of the new image to be <= than maxSurface (we add 1 to width to account for the \n characters at the end of the lines)
-  (3) (newW + 1) * newH <= maxSurface
+  We also want the are of the new image to be <= than maxChars (we add 1 to width to account for the \n characters at the end of the lines)
+  (3) (newW + 1) * newH <= maxChars
 
   We substitute (1) and (2) into (3) and solve for `scaleFactor` to find the formula below.
   */
   const scaleFactor =
-    (-height + Math.sqrt(height * height + 4 * imageArea * maxSurface)) /
+    (-height + Math.sqrt(height * height + 4 * imageArea * maxChars)) /
     (2 * imageArea);
 
   const newW = Math.floor(scaleFactor * width);
   const newH = Math.floor(scaleFactor * height);
   return [newW, newH];
 };
 
-function toAscii(alphabet) {
-  return async function* (source) {
-    for await (const chunk of source) {
-      let string = '';
+function bufferToAscii(buffer, alphabet, width) {
+  let asciiImage = '';
+  let i = 0;
 
-      for (const byte of chunk) {
-        const index = Math.floor((byte / 255) * (alphabet.length - 1));
-        string += alphabet[index];
-      }
+  for (const byte of buffer) {
+    const index = Math.floor((byte / 255) * (alphabet.length - 1));
+    asciiImage += alphabet[index];
 
-      yield string;
+    i++;
+    if (i >= width) {
+      asciiImage += '\n';
+      i = 0;
     }
-  };
-}
-
-function groupLines(lineLength) {
-  return async function* (source) {
-    let line = '';
-
-    for await (const string of source) {
-      let start = 0;
-      let end = lineLength - line.length;
-
-      while (start < string.length) {
-        const piece = string.substring(start, end);
-        line += piece;
-
-        start += piece.length;
-        end += piece.length;
+  }
 
-        if (line.length >= lineLength) {
-          yield line + '\n';
-          line = '';
-        }
-      }
-    }
-  };
+  return asciiImage;
 }
 
-export const urlToAscii = async (
-  url,
-  originalWidth,
-  originalHeight,
-  maxChars
-) => {
+export const urlToAscii = async (url, maxChars) => {
+  const imageResponse = await got(url, { responseType: 'buffer' });
+  const meta = await sharp(imageResponse.body).metadata();
+
   const [width, height] = calculateSize(
-    originalWidth,
+    meta.width,
 
     // Since pixels are square but character are not, we must squish the image so that it doesn't look stretched after being converted to ASCII
     // TODO: calculate an accurate value, this value was just eyeballed
-    originalHeight * 0.4,
+    meta.height * 0.4,
     maxChars
   );
 
-  const imageTransformer = sharp()
+  const transformedBuffer = await sharp(imageResponse.body)
     .resize({
       width,
       height,
@@ -101,23 +74,8 @@ export const urlToAscii = async (
     .normalise()
     .sharpen() // makes the edges look a bit better
     .toColorspace('b-w')
-    .raw();
-
-  const destination = new PassThrough();
-
-  const promise = pipeline(
-    got.stream(url),
-    imageTransformer,
-    toAscii(chars),
-    groupLines(width),
-    destination
-  );
+    .raw()
+    .toBuffer();
 
-  let asciiImage = '';
-  for await (const line of destination) {
-    asciiImage += line;
-  }
-
-  await promise;
-  return asciiImage;
+  return bufferToAscii(transformedBuffer, chars, width);
 };