Add support for GIF images

Author: Duncan MacKenzie

lib/image.js

@@ -6,9 +6,10 @@ By Devon Govett
 import fs from 'fs'
 import JPEG from './image/jpeg'
 import PNG from './image/png'
+import GIF from './image/gif'
 
 class PDFImage {
-  static open(src, label) {
+  static open(src, label, options) {
     let data
     if (Buffer.isBuffer(src)) {
       data = src
@@ -27,9 +28,11 @@ class PDFImage {
     }
 
     if (data[0] === 0xff && data[1] === 0xd8) {
-      return new JPEG(data, label)
+      return new JPEG(data, label, options)
     } else if (data[0] === 0x89 && data.toString('ascii', 1, 4) === 'PNG') {
-      return new PNG(data, label)
+      return new PNG(data, label, options)
+    } else if (data[0] === 71 && data[1] === 73 && data[2] === 70) {
+      return new GIF(data, label, options)
     } else {
       throw new Error('Unknown image format.')
     }

lib/image/gif.js

@@ -0,0 +1,45 @@
+const COLOR_SPACE_MAP = {
+  1: 'DeviceGray',
+  3: 'DeviceRGB',
+  4: 'DeviceCMYK'
+}
+class GIF {
+  constructor(data, label, { width, height } = {}) {
+    this.data = data;
+    this.label = label;
+
+    // validate data integrity
+
+    // assign bits per component to this.bits
+    this.bits = 8;
+
+    // assign image width and height to this.width and this.height
+    this.width = width;
+    this.height = height;
+
+    this.colorSpace = COLOR_SPACE_MAP[3];
+
+    this.obj = null;
+  }
+
+  embed(document) {
+    if (this.obj) { return; }
+
+    this.obj = document.ref({
+      Type: 'XObject',
+      Subtype: 'Image',
+      BitsPerComponent: this.bits,
+      Width: this.width,
+      Height: this.height,
+      ColorSpace: this.colorSpace,
+      Filter: 'DCTDecode'
+    });
+
+    this.obj.end(this.data);
+
+    // free memory
+    return this.data = null;
+  }
+};
+
+export default GIF;

lib/mixins/images.js

@@ -25,7 +25,7 @@ export default {
       if (src.width && src.height) {
         image = src;
       } else {
-        image = this.openImage(src);
+        image = this.openImage(src, { width: options.width, height: options.height });
       }
     }
 
@@ -102,14 +102,14 @@ export default {
     return this;
   },
 
-  openImage(src) {
+  openImage(src, options) {
     let image;
     if (typeof src === 'string') {
       image = this._imageRegistry[src];
     }
 
     if (!image) {
-      image = PDFImage.open(src, `I${++this._imageCount}`);
+      image = PDFImage.open(src, `I${++this._imageCount}`, options);
       if (typeof src === 'string') {
         this._imageRegistry[src] = image;
       }