diff --git a/index.js b/index.js
index 30d3497..24f1bc5 100644
--- a/index.js
+++ b/index.js
@@ -75,8 +75,11 @@ function gm (source, height, color) {
     var ret = inputFromStdin ? '-' : this.source;
 
     const fileNameProvied = typeof height === 'string';
-    if (inputFromStdin && fileNameProvied && /\.ico$/i.test(this.source)) {
-      ret = `ico:-`;
+    if (inputFromStdin && fileNameProvied) {
+      const extensionMatch = this.source.match(/\.(avi|apng|avif|bmp|cgm|dcm|epdf|epi|eps2?|eps3|epsf|ept|fax|fpx|g3|gif87?|ico|jpe?g|mng|mpeg|png|pdf|ps2?|ps3|svg|tiff?|wbmp|webp)$/i);
+      if (extensionMatch) {
+        ret = `${extensionMatch[1].toLowerCase()}:-`;
+      }
     }
 
     if (ret && this.sourceFrames) ret += this.sourceFrames;
diff --git a/test/fixtures/test.pdf b/test/fixtures/test.pdf
new file mode 100644
index 0000000..982f6ea
Binary files /dev/null and b/test/fixtures/test.pdf differ
diff --git a/test/pdf.js b/test/pdf.js
new file mode 100644
index 0000000..a2c84ec
--- /dev/null
+++ b/test/pdf.js
@@ -0,0 +1,15 @@
+const assert = require('assert');
+const path = require('path');
+const fs = require('fs')
+
+module.exports = function (_, dir, finish, gm, imageMagick) {
+    if (!gm.integration)  return finish();
+
+    var imagePath = path.join(__dirname, 'fixtures', 'test.pdf');
+    var inputStream = fs.createReadStream(imagePath);
+    gm(inputStream, 'test.pdf').options({ imageMagick }).identify('%w %h', function(err, value) {
+        if (err) return finish(err);
+        assert.equal(value, '612 792');
+        finish();
+    });
+}
diff --git a/test/resizeAndAutoOrientFromBuffer.js b/test/resizeAndAutoOrientFromBuffer.js
index c388d12..ab58744 100755
--- a/test/resizeAndAutoOrientFromBuffer.js
+++ b/test/resizeAndAutoOrientFromBuffer.js
@@ -9,7 +9,7 @@ module.exports = function (_, dir, finish, gm, imageMagick) {
 
   var buf = fs.readFileSync(original);
 
-  var m = gm(buf, 'resizefrombuffer.jpg')
+  var m = gm(buf)
   .options({imageMagick})
   .autoOrient()
   .resize('20%')
diff --git a/test/resizeBuffer.js b/test/resizeBuffer.js
index e021daf..3e62526 100755
--- a/test/resizeBuffer.js
+++ b/test/resizeBuffer.js
@@ -15,7 +15,7 @@ module.exports = function (_, dir, finish, gm, imageMagick) {
 
   var args = m.args();
   assert.equal('convert', args[0]);
-  assert.equal('-', args[1]);
+  assert.equal('jpg:-', args[1]);
   assert.equal('-resize', args[2]);
   if (m._options.imageMagick) {
     assert.equal('48%', args[3]);