feat: add tiff size detection support (#3)

Co-authored-by: Pooya Parsa <[email protected]>

src/types/tiff.ts

@@ -1,15 +1,101 @@
 // based on http://www.compix.com/fileformattif.htm
+// TO-DO: support big-endian as well
+import { readUInt, toHexString, toUTF8String } from "./utils";
 import type { IImage } from "./interface";
-import { toHexString } from "./utils";
+
+// Read IFD (image-file-directory) into a buffer
+function readIFD(buffer: Uint8Array, isBigEndian: boolean) {
+  const ifdOffset = readUInt(buffer, 32, 4, isBigEndian);
+
+  // read only till the end of the file
+  let bufferSize = 1024;
+  const fileSize = buffer.length;
+  if (ifdOffset + bufferSize > fileSize) {
+    bufferSize = fileSize - ifdOffset - 10;
+  }
+
+  return buffer.slice(ifdOffset + 2, ifdOffset + 2 + bufferSize);
+}
+
+// TIFF values seem to be messed up on Big-Endian, this helps
+function readValue(buffer: Uint8Array, isBigEndian: boolean): number {
+  const low = readUInt(buffer, 16, 8, isBigEndian);
+  const high = readUInt(buffer, 16, 10, isBigEndian);
+  return (high << 16) + low;
+}
+
+// move to the next tag
+function nextTag(buffer: Uint8Array) {
+  if (buffer.length > 24) {
+    return buffer.slice(12);
+  }
+}
+
+// Extract IFD tags from TIFF metadata
+function extractTags(buffer: Uint8Array, isBigEndian: boolean) {
+  const tags: { [key: number]: number } = {};
+
+  let temp: Uint8Array | undefined = buffer;
+  while (temp && temp.length > 0) {
+    const code = readUInt(temp, 16, 0, isBigEndian);
+    const type = readUInt(temp, 16, 2, isBigEndian);
+    const length = readUInt(temp, 32, 4, isBigEndian);
+
+    // 0 means end of IFD
+    if (code === 0) {
+      break;
+    } else {
+      // 256 is width, 257 is height
+      // if (code === 256 || code === 257) {
+      if (length === 1 && (type === 3 || type === 4)) {
+        tags[code] = readValue(temp, isBigEndian);
+      }
+
+      // move to the next tag
+      temp = nextTag(temp);
+    }
+  }
+
+  return tags;
+}
+
+// Test if the TIFF is Big Endian or Little Endian
+function determineEndianness(input: Uint8Array) {
+  const signature = toUTF8String(input, 0, 2);
+  if (signature === "II") {
+    return "LE";
+  } else if (signature === "MM") {
+    return "BE";
+  }
+}
 
 const signatures = new Set([
-  "492049", // ?
+  // '492049', // currently not supported
   "49492a00", // Little endian
   "4d4d002a", // Big Endian
-  "4d4d002a", // BigTIFF > 4GB. currently not supported
+  // '4d4d002a', // BigTIFF > 4GB. currently not supported
 ]);
 
 export const TIFF: IImage = {
   validate: (input) => signatures.has(toHexString(input, 0, 4)),
-  calculate: () => ({ width: undefined, height: undefined }),
+
+  calculate(input) {
+    // Determine BE/LE
+    const isBigEndian = determineEndianness(input) === "BE";
+
+    // read the IFD
+    const ifdBuffer = readIFD(input, isBigEndian);
+
+    // extract the tags from the IFD
+    const tags = extractTags(ifdBuffer, isBigEndian);
+
+    const width = tags[256];
+    const height = tags[257];
+
+    if (!width || !height) {
+      throw new TypeError("Invalid Tiff. Missing tags");
+    }
+
+    return { height, width };
+  },
 };

test/fixtures/valid/tiff/big-endian.tiff.meta

@@ -1,5 +1,5 @@
 {
-  "height": undefined,
+  "height": 456,
   "type": "tiff",
-  "width": undefined,
+  "width": 123,
 }

test/fixtures/valid/tiff/jpeg.tiff.meta

@@ -1,5 +1,5 @@
 {
-  "height": undefined,
+  "height": 456,
   "type": "tiff",
-  "width": undefined,
+  "width": 123,
 }

test/fixtures/valid/tiff/little-endian.tiff.meta

@@ -1,5 +1,5 @@
 {
-  "height": undefined,
+  "height": 456,
   "type": "tiff",
-  "width": undefined,
+  "width": 123,
 }