Add support for loading images through ImageMagick as a buffer

index.js

@@ -83,11 +83,13 @@ var Sharp = function(input) {
       (input[0] === 0x52 && input[1] === 0x49) ||
       // TIFF
       (input[0] === 0x4D && input[1] === 0x4D && input[2] === 0x00 && (input[3] === 0x2A || input[3] === 0x2B)) ||
-      (input[0] === 0x49 && input[1] === 0x49 && (input[2] === 0x2A || input[2] === 0x2B) && input[3] === 0x00)
+      (input[0] === 0x49 && input[1] === 0x49 && (input[2] === 0x2A || input[2] === 0x2B) && input[3] === 0x00) ||
+      // GIF
+      (input[0] === 0x47 && input[1] === 0x49 && input[2] === 0x46 && input[3] === 0x38 && (input[4] === 0x37 || input[4] === 0x39) && input[5] === 0x61)
     ) {
       this.options.bufferIn = input;
     } else {
-      throw new Error('Buffer contains an unsupported image format. JPEG, PNG, WebP and TIFF are currently supported.');
+      throw new Error('Buffer contains an unsupported image format. JPEG, PNG, WebP, TIFF and GIF are currently supported.');
     }
   } else {
     // input=stream

src/common.cc

@@ -43,6 +43,15 @@ namespace sharp {
     );
   }
 
+  static bool buffer_is_gif(char *buffer, size_t len) {
+    return (
+      len >= 6 && (
+          (buffer[0] == 'G' && buffer[1] == 'I' && buffer[2] == 'F' &&
+            buffer[3] == '8' && (buffer[4] == '7' || buffer[4] == '9') && buffer[5] == 'a')
+        )
+    );
+  }
+
   /*
     Determine image format of a buffer.
   */
@@ -57,6 +66,8 @@ namespace sharp {
         imageType = ImageType::WEBP;
       } else if (buffer_is_tiff(static_cast<char*>(buffer), length)) {
         imageType = ImageType::TIFF;
+      } else if (buffer_is_gif(static_cast<char*>(buffer), length)) {
+        imageType = ImageType::MAGICK;
       }
     }
     return imageType;
@@ -75,6 +86,10 @@ namespace sharp {
       vips_webpload_buffer(buffer, length, &image, "access", access, NULL);
     } else if (imageType == ImageType::TIFF) {
       vips_tiffload_buffer(buffer, length, &image, "access", access, NULL);
+#if (VIPS_MAJOR_VERSION >= 8 && VIPS_MINOR_VERSION >= 0)
+    } else if (imageType == ImageType::MAGICK) {
+      vips_magickload_buffer(buffer, length, &image, "access", access, NULL);
+#endif
     }
     return image;
   }

test/unit/io.js

@@ -537,6 +537,24 @@ describe('Input/output', function() {
     });
   }
 
+  if (semver.gte(sharp.libvipsVersion(), '8.0.0')) {
+    it('Load GIF from Buffer [libvips ' + sharp.libvipsVersion() + '>=8.0.0]', function(done) {
+      var inputGifBuffer = fs.readFileSync(fixtures.inputGif);
+      sharp(inputGifBuffer)
+        .resize(320, 240)
+        .jpeg()
+        .toBuffer(function(err, data, info) {
+          if (err) throw err;
+          assert.strictEqual(true, data.length > 0);
+          assert.strictEqual(data.length, info.size);
+          assert.strictEqual('jpeg', info.format);
+          assert.strictEqual(320, info.width);
+          assert.strictEqual(240, info.height);
+          done();
+        });
+    });
+  }
+
   if (semver.gte(sharp.libvipsVersion(), '7.42.0')) {
     describe('Ouput raw, uncompressed image data [libvips ' + sharp.libvipsVersion() + '>=7.42.0]', function() {
       it('1 channel greyscale image', function(done) {