Fix PdfImage constructor without alpha channel

@@ -10,6 +10,7 @@
 - Allow saving an unmodified document
 - Table cell: dynamic widget [Shahriyar Aghajani]
 - Move Table.fromTextArray to TableHelper.fromTextArray
+- Fix PdfImage constructor without alpha channel [Tomasz Gucio]
 
 ## 3.10.1
 

@@ -97,10 +97,18 @@ class PdfImage extends PdfXObject {
     final h = height;
     final s = w * h;
     final out = Uint8List(s * 3);
-    for (var i = 0; i < s; i++) {
-      out[i * 3] = image[i * 4];
-      out[i * 3 + 1] = image[i * 4 + 1];
-      out[i * 3 + 2] = image[i * 4 + 2];
+    if (alpha) {
+      for (var i = 0; i < s; i++) {
+        out[i * 3] = image[i * 4];
+        out[i * 3 + 1] = image[i * 4 + 1];
+        out[i * 3 + 2] = image[i * 4 + 2];
+      }
+    } else {
+      for (var i = 0; i < s; i++) {
+        out[i * 3] = image[i * 3];
+        out[i * 3 + 1] = image[i * 3 + 1];
+        out[i * 3 + 2] = image[i * 3 + 2];
+      }
     }
 
     im.buf.putBytes(out);

+/*
+ * Copyright (C) 2017, David PHAM-VAN <dev.nfet.net@gmail.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import 'dart:typed_data';
+
+import 'package:pdf/pdf.dart';
+import 'package:pdf/src/priv.dart';
+import 'package:test/test.dart';
+
+const kRedValue = 110;
+const kGreenValue = 120;
+const kBlueValue = 130;
+const kAlphaValue = 200;
+
+Uint8List createTestImage(int width, int height, {bool withAlpha = true}) {
+  final channelCount = withAlpha ? 4 : 3;
+  final img = Uint8List(width * height * channelCount);
+  for (var pixelIndex = 0; pixelIndex < width * height; pixelIndex++) {
+    img[pixelIndex * channelCount] = kRedValue;
+    img[pixelIndex * channelCount + 1] = kGreenValue;
+    img[pixelIndex * channelCount + 2] = kBlueValue;
+    if (channelCount == 4) {
+      img[pixelIndex * channelCount + 3] = kAlphaValue;
+    }
+  }
+
+  return img;
+}
+
+void main() {
+  test('PdfImage constructor with alpha channel', () async {
+    final img = createTestImage(300, 200);
+
+    final pdf = PdfDocument();
+
+    final image = PdfImage(
+      pdf,
+      image: img.buffer.asUint8List(),
+      width: 300,
+      height: 200,
+    );
+
+    expect(image.params['/Width'], const PdfNum(300));
+    expect(image.params['/Height'], const PdfNum(200));
+    expect(image.params['/SMask'], isA<PdfIndirect>());
+
+    final buf = image.buf.output();
+    for (var pixelIndex = 0; pixelIndex < 300 * 200; pixelIndex++) {
+      expect(buf[pixelIndex * 3], kRedValue);
+      expect(buf[pixelIndex * 3 + 1], kGreenValue);
+      expect(buf[pixelIndex * 3 + 2], kBlueValue);
+    }
+  });
+
+  test('PdfImage constructor without alpha channel', () async {
+    final img = createTestImage(300, 200, withAlpha: false);
+
+    final pdf = PdfDocument();
+
+    final image = PdfImage(
+      pdf,
+      image: img.buffer.asUint8List(),
+      width: 300,
+      height: 200,
+      alpha: false,
+    );
+
+    expect(image.params['/Width'], const PdfNum(300));
+    expect(image.params['/Height'], const PdfNum(200));
+    expect(image.params['/SMask'], isNull);
+
+    final buf = image.buf.output();
+    for (var pixelIndex = 0; pixelIndex < 300 * 200; pixelIndex++) {
+      expect(buf[pixelIndex * 3], kRedValue);
+      expect(buf[pixelIndex * 3 + 1], kGreenValue);
+      expect(buf[pixelIndex * 3 + 2], kBlueValue);
+    }
+  });
+}