1 files changed, 112 insertions, 0 deletions
diff --git a/app/javascript/mastodon/blurhash.js b/app/javascript/mastodon/blurhash.js
new file mode 100644
index 000000000..5adcc3e77
--- /dev/null
+++ b/app/javascript/mastodon/blurhash.js
@@ -0,0 +1,112 @@
+const DIGIT_CHARACTERS = [
+  '0',
+  '1',
+  '2',
+  '3',
+  '4',
+  '5',
+  '6',
+  '7',
+  '8',
+  '9',
+  'A',
+  'B',
+  'C',
+  'D',
+  'E',
+  'F',
+  'G',
+  'H',
+  'I',
+  'J',
+  'K',
+  'L',
+  'M',
+  'N',
+  'O',
+  'P',
+  'Q',
+  'R',
+  'S',
+  'T',
+  'U',
+  'V',
+  'W',
+  'X',
+  'Y',
+  'Z',
+  'a',
+  'b',
+  'c',
+  'd',
+  'e',
+  'f',
+  'g',
+  'h',
+  'i',
+  'j',
+  'k',
+  'l',
+  'm',
+  'n',
+  'o',
+  'p',
+  'q',
+  'r',
+  's',
+  't',
+  'u',
+  'v',
+  'w',
+  'x',
+  'y',
+  'z',
+  '#',
+  '$',
+  '%',
+  '*',
+  '+',
+  ',',
+  '-',
+  '.',
+  ':',
+  ';',
+  '=',
+  '?',
+  '@',
+  '[',
+  ']',
+  '^',
+  '_',
+  '{',
+  '|',
+  '}',
+  '~',
+];
+
+export const decode83 = (str) => {
+  let value = 0;
+  let c, digit;
+
+  for (let i = 0; i < str.length; i++) {
+    c = str[i];
+    digit = DIGIT_CHARACTERS.indexOf(c);
+    value = value * 83 + digit;
+  }
+
+  return value;
+};
+
+export const intToRGB = int => ({
+  r: Math.max(0, (int >> 16)),
+  g: Math.max(0, (int >> 8) & 255),
+  b: Math.max(0, (int & 255)),
+});
+
+export const getAverageFromBlurhash = blurhash => {
+  if (!blurhash) {
+    return null;
+  }
+
+  return intToRGB(decode83(blurhash.slice(2, 6)));
+};