Improve gradient functions

@@ -13,6 +13,7 @@
 - Opt-out from dart library
 - Improve graphic operations
 - Automatically calculate Shape() bounding box
+- Improve gradient functions
 
 ## 1.12.0
 

@@ -32,6 +32,7 @@ export 'src/info.dart';
 export 'src/outline.dart';
 export 'src/page.dart';
 export 'src/page_format.dart';
+export 'src/pattern.dart';
 export 'src/point.dart';
 export 'src/rect.dart';
 export 'src/shading.dart';

@@ -258,7 +258,7 @@ class PdfSecString extends PdfString {
 }
 
 class PdfName extends PdfDataType {
-  const PdfName(this.value);
+  const PdfName(this.value) : assert(value != null);
 
   final String value;
 

@@ -24,35 +24,103 @@ import 'object_stream.dart';
 
 abstract class PdfBaseFunction extends PdfObject {
   PdfBaseFunction(PdfDocument pdfDocument) : super(pdfDocument);
+
+  factory PdfBaseFunction.colorsAndStops(
+    PdfDocument pdfDocument,
+    List<PdfColor> colors, [
+    List<double> stops,
+  ]) {
+    if (stops == null || stops.isEmpty) {
+      return PdfFunction.fromColors(pdfDocument, colors);
+    }
+
+    final _colors = List<PdfColor>.from(colors);
+    final _stops = List<double>.from(stops);
+
+    final fn = <PdfFunction>[];
+    var lc = _colors.first;
+
+    if (_stops[0] > 0) {
+      _colors.insert(0, lc);
+      _stops.insert(0, 0);
+    }
+
+    if (_stops.last < 1) {
+      _colors.add(_colors.last);
+      _stops.add(1);
+    }
+
+    if (_stops.length != _colors.length) {
+      throw Exception(
+          'The number of colors in a gradient must match the number of stops');
+    }
+
+    for (final c in _colors.sublist(1)) {
+      fn.add(PdfFunction.fromColors(pdfDocument, <PdfColor>[lc, c]));
+      lc = c;
+    }
+
+    return PdfStitchingFunction(
+      pdfDocument,
+      functions: fn,
+      bounds: _stops.sublist(1, _stops.length - 1),
+      domainStart: 0,
+      domainEnd: 1,
+    );
+  }
 }
 
 class PdfFunction extends PdfObjectStream implements PdfBaseFunction {
   PdfFunction(
     PdfDocument pdfDocument, {
-    this.colors,
+    this.data,
+    this.bitsPerSample = 8,
+    this.order = 1,
+    this.domain = const <num>[0, 1],
+    this.range = const <num>[0, 1],
   }) : super(pdfDocument);
 
-  final List<PdfColor> colors;
-
-  @override
-  void prepare() {
+  factory PdfFunction.fromColors(
+      PdfDocument pdfDocument, List<PdfColor> colors) {
+    final data = <int>[];
     for (final color in colors) {
-      buf.putBytes(<int>[
-        (color.red * 255.0).round() & 0xff,
-        (color.green * 255.0).round() & 0xff,
-        (color.blue * 255.0).round() & 0xff,
-      ]);
+      data.add((color.red * 255.0).round() & 0xff);
+      data.add((color.green * 255.0).round() & 0xff);
+      data.add((color.blue * 255.0).round() & 0xff);
     }
+    return PdfFunction(
+      pdfDocument,
+      order: 3,
+      data: data,
+      range: const <num>[0, 1, 0, 1, 0, 1],
+    );
+  }
+
+  final List<int> data;
+
+  final int bitsPerSample;
+
+  final int order;
+
+  final List<num> domain;
+
+  final List<num> range;
 
+  @override
+  void prepare() {
+    buf.putBytes(data);
     super.prepare();
 
     params['/FunctionType'] = const PdfNum(0);
-    params['/BitsPerSample'] = const PdfNum(8);
-    params['/Order'] = const PdfNum(3);
-    params['/Domain'] = PdfArray.fromNum(const <num>[0, 1]);
-    params['/Range'] = PdfArray.fromNum(const <num>[0, 1, 0, 1, 0, 1]);
-    params['/Size'] = PdfArray.fromNum(<int>[colors.length]);
+    params['/BitsPerSample'] = PdfNum(bitsPerSample);
+    params['/Order'] = PdfNum(order);
+    params['/Domain'] = PdfArray.fromNum(domain);
+    params['/Range'] = PdfArray.fromNum(range);
+    params['/Size'] = PdfArray.fromNum(<int>[data.length ~/ order]);
   }
+
+  @override
+  String toString() => '$runtimeType $bitsPerSample $order $data';
 }
 
 class PdfStitchingFunction extends PdfBaseFunction {
@@ -86,4 +154,8 @@ class PdfStitchingFunction extends PdfBaseFunction {
     params['/Encode'] = PdfArray.fromNum(
         List<int>.generate(functions.length * 2, (int i) => i % 2));
   }
+
+  @override
+  String toString() =>
+      '$runtimeType $domainStart $bounds $domainEnd $functions';
 }

@@ -31,8 +31,7 @@ class PdfGraphicState {
   /// The opacity to apply to this graphic state
   final double opacity;
 
-  @protected
-  PdfDict _output() {
+  PdfDict output() {
     final params = PdfDict();
 
     if (opacity != null) {
@@ -79,7 +78,7 @@ class PdfGraphicStates extends PdfObject {
     super.prepare();
 
     for (var index = 0; index < _states.length; index++) {
-      params['$_prefix$index'] = _states[index]._output();
+      params['$_prefix$index'] = _states[index].output();
     }
   }
 }

@@ -19,6 +19,7 @@ import 'document.dart';
 import 'font.dart';
 import 'graphic_state.dart';
 import 'object.dart';
+import 'pattern.dart';
 import 'shading.dart';
 import 'xobject.dart';
 
@@ -37,13 +38,16 @@ mixin PdfGraphicStream on PdfObject {
   bool knockoutTransparency = false;
 
   /// The fonts associated with this page
-  final Map<String, PdfFont> fonts = <String, PdfFont>{};
+  final fonts = <String, PdfFont>{};
 
-  /// The fonts associated with this page
-  final Map<String, PdfShading> shading = <String, PdfShading>{};
+  /// The shaders associated with this page
+  final shading = <String, PdfShading>{};
+
+  /// The shaders associated with this page
+  final patterns = <String, PdfPattern>{};
 
   /// The xobjects or other images in the pdf
-  final Map<String, PdfXObject> xObjects = <String, PdfXObject>{};
+  final xObjects = <String, PdfXObject>{};
 
   /// Add a font to this graphic object
   void addFont(PdfFont font) {
@@ -59,6 +63,13 @@ mixin PdfGraphicStream on PdfObject {
     }
   }
 
+  /// Add a pattern to this graphic object
+  void addPattern(PdfPattern pattern) {
+    if (!patterns.containsKey(pattern.name)) {
+      patterns[pattern.name] = pattern;
+    }
+  }
+
   /// Add an XObject to this graphic object
   void addXObject(PdfXObject object) {
     if (!xObjects.containsKey(object.name)) {
@@ -99,11 +110,16 @@ mixin PdfGraphicStream on PdfObject {
       resources['/Font'] = PdfDict.fromObjectMap(fonts);
     }
 
-    // shading
+    // shaders
     if (shading.isNotEmpty) {
       resources['/Shading'] = PdfDict.fromObjectMap(shading);
     }
 
+    // patterns
+    if (patterns.isNotEmpty) {
+      resources['/Pattern'] = PdfDict.fromObjectMap(patterns);
+    }
+
     // Now the XObjects
     if (xObjects.isNotEmpty) {
       resources['/XObject'] = PdfDict.fromObjectMap(xObjects);

@@ -28,6 +28,7 @@ import 'graphic_state.dart';
 import 'graphic_stream.dart';
 import 'image.dart';
 import 'page.dart';
+import 'pattern.dart';
 import 'rect.dart';
 import 'shading.dart';
 import 'stream.dart';
@@ -86,10 +87,14 @@ enum PdfTextRenderingMode {
 
 @immutable
 class _PdfGraphicsContext {
-  const _PdfGraphicsContext({@required this.ctm}) : assert(ctm != null);
+  const _PdfGraphicsContext({
+    @required this.ctm,
+  }) : assert(ctm != null);
   final Matrix4 ctm;
 
-  _PdfGraphicsContext copy() => _PdfGraphicsContext(ctm: ctm.clone());
+  _PdfGraphicsContext copy() => _PdfGraphicsContext(
+        ctm: ctm.clone(),
+      );
 }
 
 /// Pdf drawing operations
@@ -346,6 +351,20 @@ class PdfGraphics {
     }
   }
 
+  /// Sets the fill pattern for drawing
+  void setFillPattern(PdfPattern pattern) {
+    // The shader needs to be registered in the page resources
+    _page.addPattern(pattern);
+    buf.putString('/Pattern cs${pattern.name} scn\n');
+  }
+
+  /// Sets the stroke pattern for drawing
+  void setStrokePattern(PdfPattern pattern) {
+    // The shader needs to be registered in the page resources
+    _page.addPattern(pattern);
+    buf.putString('/Pattern CS${pattern.name} SCN\n');
+  }
+
   /// Set the graphic state for drawing
   void setGraphicState(PdfGraphicState state) {
     final name = _page.stateName(state);

+/*
+ * 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 'package:meta/meta.dart';
+import 'package:pdf/src/data_types.dart';
+import 'package:vector_math/vector_math_64.dart';
+
+import 'document.dart';
+import 'graphic_state.dart';
+import 'object.dart';
+import 'shading.dart';
+
+abstract class PdfPattern extends PdfObject {
+  PdfPattern(PdfDocument pdfDocument, this.patternType, this.matrix)
+      : super(pdfDocument);
+
+  /// Name of the Pattern object
+  String get name => '/P$objser';
+
+  final int patternType;
+
+  final Matrix4 matrix;
+
+  @override
+  void prepare() {
+    super.prepare();
+
+    params['/PatternType'] = PdfNum(patternType);
+
+    if (matrix != null) {
+      final s = matrix.storage;
+      params['/Matrix'] =
+          PdfArray.fromNum(<double>[s[0], s[1], s[4], s[5], s[12], s[13]]);
+    }
+  }
+}
+
+class PdfShadingPattern extends PdfPattern {
+  PdfShadingPattern(
+    PdfDocument pdfDocument, {
+    @required this.shading,
+    Matrix4 matrix,
+    this.graphicState,
+  })  : assert(shading != null),
+        super(pdfDocument, 2, matrix);
+
+  final PdfShading shading;
+
+  final PdfGraphicState graphicState;
+
+  @override
+  void prepare() {
+    super.prepare();
+
+    params['/Shading'] = shading.ref();
+
+    if (graphicState != null) {
+      params['/ExtGState'] = graphicState.output();
+    }
+  }
+}

@@ -231,38 +231,6 @@ abstract class Gradient {
   /// A list of values from 0.0 to 1.0 that denote fractions along the gradient.
   final List<double> stops;
 
-  PdfBaseFunction _buildFunction(
-    Context context,
-    List<PdfColor> colors,
-    List<double> stops,
-  ) {
-    if (stops == null) {
-      return PdfFunction(
-        context.document,
-        colors: colors,
-      );
-    }
-
-    final fn = <PdfFunction>[];
-
-    var lc = colors.first;
-    for (final c in colors.sublist(1)) {
-      fn.add(PdfFunction(
-        context.document,
-        colors: <PdfColor>[lc, c],
-      ));
-      lc = c;
-    }
-
-    return PdfStitchingFunction(
-      context.document,
-      functions: fn,
-      bounds: stops.sublist(1, stops.length - 1),
-      domainStart: stops.first,
-      domainEnd: stops.last,
-    );
-  }
-
   void paint(Context context, PdfRect box);
 }
 
@@ -311,7 +279,11 @@ class LinearGradient extends Gradient {
           context.document,
           shadingType: PdfShadingType.axial,
           boundingBox: box,
-          function: _buildFunction(context, colors, stops),
+          function: PdfBaseFunction.colorsAndStops(
+            context.document,
+            colors,
+            stops,
+          ),
           start: begin.withinRect(box),
           end: end.withinRect(box),
           extendStart: true,
@@ -384,7 +356,11 @@ class RadialGradient extends Gradient {
           context.document,
           shadingType: PdfShadingType.radial,
           boundingBox: box,
-          function: _buildFunction(context, colors, stops),
+          function: PdfBaseFunction.colorsAndStops(
+            context.document,
+            colors,
+            stops,
+          ),
           start: _focal.withinRect(box),
           end: center.withinRect(box),
           radius0: focalRadius * _radius,

@@ -60,7 +60,7 @@ void printTextTtf(
 
 void main() {
   test('Pdf TrueType', () {
-    final pdf = PdfDocument(compress: false);
+    final pdf = PdfDocument();
     final page = PdfPage(pdf, pageFormat: const PdfPageFormat(500, 300));
 
     final g = page.getGraphics();