Finalization of axial shading

PdfForQtLib/sources/pdfcolorspaces.cpp

@@ -275,6 +275,40 @@ PDFColor PDFAbstractColorSpace::convertToColor(const std::vector<PDFReal>& compo
     return result;
 }
 
+bool PDFAbstractColorSpace::isColorEqual(const PDFColor& color1, const PDFColor& color2, PDFReal tolerance)
+{
+    const size_t size = color1.size();
+    if (size != color2.size())
+    {
+        return false;
+    }
+
+    for (size_t i = 0; i < size; ++i)
+    {
+        if (std::fabs(color1[i] - color2[i]) > tolerance)
+        {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+PDFColor PDFAbstractColorSpace::mixColors(const PDFColor& color1, const PDFColor& color2, PDFReal ratio)
+{
+    const size_t size = color1.size();
+    Q_ASSERT(size == color2.size());
+
+    PDFColor result;
+    result.resize(size);
+    for (size_t i = 0; i < size; ++i)
+    {
+        result[i] = color1[i] * ratio + color2[i] * (1.0 - ratio);
+    }
+
+    return result;
+}
+
 PDFColorSpacePointer PDFAbstractColorSpace::createColorSpaceImpl(const PDFDictionary* colorSpaceDictionary,
                                                                  const PDFDocument* document,
                                                                  const PDFObject& colorSpace,

PdfForQtLib/sources/pdfcolorspaces.h

@@ -236,6 +236,20 @@ public:
     /// Converts a vector of real numbers to the PDFColor
     static PDFColor convertToColor(const std::vector<PDFReal>& components);
 
+    /// Returns true, if two colors are equal (considering the tolerance). So, if one
+    /// of the color components differs more than \p tolerance from the another, then
+    /// false is returned. If colors have different number of components, false is returned.
+    /// \param color1 First color
+    /// \param color2 Second color
+    /// \param tolerance Color tolerance
+    static bool isColorEqual(const PDFColor& color1, const PDFColor& color2, PDFReal tolerance);
+
+    /// Mix colors according the given ratio.
+    /// \param color1 First color
+    /// \param color2 Second color
+    /// \param ratio Mixing ratio
+    static PDFColor mixColors(const PDFColor& color1, const PDFColor& color2, PDFReal ratio);
+
 protected:
     /// Clips the color component to range [0, 1]
     static constexpr PDFColorComponent clip01(PDFColorComponent component) { return qBound<PDFColorComponent>(0.0, component, 1.0); }

PdfForQtLib/sources/pdfflatarray.h

@@ -158,6 +158,25 @@ public:
     /// Erases the last element from the array
     inline void pop_back() { resize(size() - 1); }
 
+    bool operator==(const PDFFlatArray& other) const
+    {
+        const size_t size = this->size();
+        if (size != other.size())
+        {
+            return false;
+        }
+
+        for (size_t i = 0; i < size; ++i)
+        {
+            if ((*this)[i] != other[i])
+            {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
 private:
     size_t getFlatBlockSize() const { return m_flatBlockItemCount; }
 

PdfForQtLib/sources/pdfglobal.h

@@ -42,12 +42,18 @@ using PDFReal = double;
 
 constexpr PDFInteger PDF_INTEGER_MIN = std::numeric_limits<int64_t>::min() / 100;
 constexpr PDFInteger PDF_INTEGER_MAX = std::numeric_limits<int64_t>::max() / 100;
+constexpr PDFReal PDF_EPSILON = 0.000001;
 
 static constexpr bool isValidInteger(PDFInteger integer)
 {
     return integer >= PDF_INTEGER_MIN && integer <= PDF_INTEGER_MAX;
 }
 
+static inline bool isZero(PDFReal value)
+{
+    return std::fabs(value) < PDF_EPSILON;
+}
+
 /// This structure represents a reference to the object - consisting of the
 /// object number, and generation number.
 struct PDFObjectReference

PdfForQtLib/sources/pdfpagecontentprocessor.cpp

@@ -181,7 +181,7 @@ PDFPageContentProcessor::PDFPageContentProcessor(const PDFPage* page,
                                                  const PDFDocument* document,
                                                  const PDFFontCache* fontCache,
                                                  const PDFOptionalContentActivity* optionalContentActivity,
-                                                 QMatrix patternBaseMatrix) :
+                                                 QMatrix pagePointToDevicePointMatrix) :
     m_page(page),
     m_document(document),
     m_fontCache(fontCache),
@@ -194,14 +194,15 @@ PDFPageContentProcessor::PDFPageContentProcessor(const PDFPage* page,
     m_shadingDictionary(nullptr),
     m_textBeginEndState(0),
     m_compatibilityBeginEndState(0),
-    m_patternBaseMatrix(patternBaseMatrix)
+    m_patternBaseMatrix(pagePointToDevicePointMatrix),
+    m_pagePointToDevicePointMatrix(pagePointToDevicePointMatrix)
 {
     Q_ASSERT(page);
     Q_ASSERT(document);
 
     QPainterPath pageRectPath;
     pageRectPath.addRect(m_page->getRotatedMediaBox());
-    m_pageBoundingRectDeviceSpace = patternBaseMatrix.map(pageRectPath).boundingRect();
+    m_pageBoundingRectDeviceSpace = pagePointToDevicePointMatrix.map(pageRectPath).boundingRect();
 
     initDictionaries(m_page->getResources());
 }
@@ -548,7 +549,8 @@ void PDFPageContentProcessor::processForm(const QMatrix& matrix, const QRectF& b
     m_graphicState.setCurrentTransformationMatrix(formMatrix);
     updateGraphicState();
 
-    PDFTemporaryValueChange patternMatrixGuard(&m_patternBaseMatrix, formMatrix);
+    QMatrix patternMatrix = formMatrix * m_pagePointToDevicePointMatrix;
+    PDFTemporaryValueChange patternMatrixGuard(&m_patternBaseMatrix, patternMatrix);
 
     // If the clipping box is valid, then use clipping. Clipping box is in the form coordinate system
     if (boundingBox.isValid())
@@ -2044,7 +2046,7 @@ void PDFPageContentProcessor::operatorTextSetSpacingAndShowText(PDFReal t_w, PDF
 
 void PDFPageContentProcessor::operatorShadingPaintShape(PDFPageContentProcessor::PDFOperandName name)
 {
-    QMatrix matrix = getGraphicState()->getCurrentTransformationMatrix();
+    QMatrix matrix = getCurrentWorldMatrix();
     PDFPageContentProcessorStateGuard guard(this);
     PDFTemporaryValueChange guard2(&m_patternBaseMatrix, matrix);
 

PdfForQtLib/sources/pdfpagecontentprocessor.h

@@ -46,7 +46,7 @@ public:
                                      const PDFDocument* document,
                                      const PDFFontCache* fontCache,
                                      const PDFOptionalContentActivity* optionalContentActivity,
-                                     QMatrix patternBaseMatrix);
+                                     QMatrix pagePointToDevicePointMatrix);
     virtual ~PDFPageContentProcessor();
 
     enum class Operator
@@ -413,6 +413,18 @@ protected:
     /// Returns true, if graphic content is suppressed
     bool isContentSuppressed() const;
 
+    /// Returns page point to device point matrix
+    const QMatrix& getPagePointToDevicePointMatrix() const { return m_pagePointToDevicePointMatrix; }
+
+    /// Returns base matrix for patterns
+    const QMatrix& getPatternBaseMatrix() const { return m_patternBaseMatrix; }
+
+    /// Returns current world matrix (translating actual point to the device point)
+    QMatrix getCurrentWorldMatrix() const { return getGraphicState()->getCurrentTransformationMatrix() * m_pagePointToDevicePointMatrix; }
+
+    /// Returns page bounding rectangle in device space
+    const QRectF& getPageBoundingRectDeviceSpace() const { return m_pageBoundingRectDeviceSpace; }
+
     /// Computes visibility of OCG/OCMD - returns false, if it is not suppressed,
     /// or true, if it is suppressed.
     virtual bool isContentSuppressedByOC(PDFObjectReference ocgOrOcmd);
@@ -738,6 +750,9 @@ private:
     /// with pattern matrix to get transformation from pattern space to device space.
     QMatrix m_patternBaseMatrix;
 
+    /// Matrix mapping page points to the device points
+    QMatrix m_pagePointToDevicePointMatrix;
+
     /// Bounding rectangle of pages media box in device space coordinates. If drawing rotation
     /// is zero, then it corresponds to the scaled media box of the page.
     QRectF m_pageBoundingRectDeviceSpace;

PdfForQtLib/sources/pdfpainter.cpp

@@ -16,6 +16,7 @@
 //    along with PDFForQt.  If not, see <https://www.gnu.org/licenses/>.
 
 #include "pdfpainter.h"
+#include "pdfpattern.h"
 
 #include <QPainter>
 
@@ -31,8 +32,7 @@ PDFPainter::PDFPainter(QPainter* painter,
                        const PDFOptionalContentActivity* optionalContentActivity) :
     PDFPageContentProcessor(page, document, fontCache, optionalContentActivity, pagePointToDevicePointMatrix),
     m_painter(painter),
-    m_features(features),
-    m_pagePointToDevicePointMatrix(pagePointToDevicePointMatrix)
+    m_features(features)
 {
     Q_ASSERT(painter);
     Q_ASSERT(pagePointToDevicePointMatrix.isInvertible());
@@ -60,6 +60,24 @@ void PDFPainter::performPathPainting(const QPainterPath& path, bool stroke, bool
         return;
     }
 
+    // TODO: Temporary
+    if (const PDFPatternColorSpace* ps = dynamic_cast<const PDFPatternColorSpace*>(getGraphicState()->getFillColorSpace()))
+    {
+        m_painter->save();
+        const PDFAxialShading* pattern = (PDFAxialShading*)ps->getPattern();
+        m_painter->setClipPath(path, Qt::IntersectClip);
+
+        PDFMeshQualitySettings settings;
+        settings.deviceSpaceMeshingArea = getPageBoundingRectDeviceSpace();
+        settings.userSpaceToDeviceSpaceMatrix = getPatternBaseMatrix();
+        settings.initDefaultResolution();
+
+        PDFMesh mesh = pattern->createMesh(settings);
+        mesh.paint(m_painter);
+        m_painter->restore();
+        return;
+    }
+
     // Set antialiasing
     const bool antialiasing = (text && m_features.testFlag(PDFRenderer::TextAntialiasing)) || (!text && m_features.testFlag(PDFRenderer::Antialiasing));
     m_painter->setRenderHint(QPainter::Antialiasing, antialiasing);
@@ -153,7 +171,7 @@ void PDFPainter::performUpdateGraphicsState(const PDFPageContentProcessorState&
     // If current transformation matrix has changed, then update it
     if (flags.testFlag(PDFPageContentProcessorState::StateCurrentTransformationMatrix))
     {
-        m_painter->setWorldMatrix(state.getCurrentTransformationMatrix() * m_pagePointToDevicePointMatrix, false);
+        m_painter->setWorldMatrix(getCurrentWorldMatrix(), false);
     }
 
     if (flags.testFlag(PDFPageContentProcessorState::StateStrokeColor) ||

PdfForQtLib/sources/pdfpainter.h

@@ -74,7 +74,6 @@ private:
 
     QPainter* m_painter;
     PDFRenderer::Features m_features;
-    QMatrix m_pagePointToDevicePointMatrix;
     PDFCachedItem<QPen> m_currentPen;
     PDFCachedItem<QBrush> m_currentBrush;
 };

PdfForQtLib/sources/pdfpattern.cpp

@@ -18,6 +18,10 @@
 #include "pdfpattern.h"
 #include "pdfdocument.h"
 #include "pdfexception.h"
+#include "pdfutils.h"
+#include "pdfcolorspaces.h"
+
+#include <QPainter>
 
 namespace pdf
 {
@@ -186,4 +190,261 @@ PDFPatternPtr PDFPattern::createShadingPattern(const PDFDictionary* colorSpaceDi
     return PDFPatternPtr();
 }
 
+PDFMesh PDFAxialShading::createMesh(const PDFMeshQualitySettings& settings) const
+{
+    PDFMesh mesh;
+
+    QPointF p1 = settings.userSpaceToDeviceSpaceMatrix.map(m_startPoint);
+    QPointF p2 = settings.userSpaceToDeviceSpaceMatrix.map(m_endPoint);
+
+    // Strategy: for simplification, we rotate the line clockwise so we will
+    // get the shading axis equal to the x-axis. Then we will determine the shading
+    // area and create mesh according the settings.
+    QLineF line(p1, p2);
+    const double angle = line.angleTo(QLineF(0, 0, 1, 0));
+
+    // Matrix p1p2LCS is local coordinate system of line p1-p2. It transforms
+    // points on the line to the global coordinate system. So, point (0, 0) will
+    // map onto p1 and point (length(p1-p2), 0) will map onto p2.
+    QMatrix p1p2LCS;
+    p1p2LCS.translate(p1.x(), p1.y());
+    p1p2LCS.rotate(angle);
+    QMatrix p1p2GCS = p1p2LCS.inverted();
+
+    QPointF p1m = p1p2GCS.map(p1);
+    QPointF p2m = p1p2GCS.map(p2);
+
+    Q_ASSERT(isZero(p1m.y()));
+    Q_ASSERT(isZero(p2m.y()));
+    Q_ASSERT(p1m.x() <= p2m.x());
+
+    QPainterPath meshingArea;
+    meshingArea.addPolygon(p1p2GCS.map(settings.deviceSpaceMeshingArea));
+    meshingArea.addRect(p1m.x(), p1m.y() - settings.preferredMeshResolution * 0.5, p2m.x() - p1m.x(), settings.preferredMeshResolution);
+    QRectF meshingRectangle = meshingArea.boundingRect();
+
+    PDFReal xl = meshingRectangle.left();
+    PDFReal xr = meshingRectangle.right();
+    PDFReal yt = meshingRectangle.top();
+    PDFReal yb = meshingRectangle.bottom();
+
+    // Create coordinate array filled with stops, where we will determine the color
+    std::vector<PDFReal> xCoords;
+    xCoords.reserve((xr - xl) / settings.minimalMeshResolution + 3);
+    xCoords.push_back(xl);
+    for (PDFReal x = p1m.x(); x <= p2m.x(); x += settings.minimalMeshResolution)
+    {
+        if (!qFuzzyCompare(xCoords.back(), x))
+        {
+            xCoords.push_back(x);
+        }
+    }
+    if (!qFuzzyCompare(xCoords.back(), xr))
+    {
+        xCoords.push_back(xr);
+    }
+
+    const PDFReal tAtStart = m_domainStart;
+    const PDFReal tAtEnd = m_domainEnd;
+    const PDFReal tMin = qMin(tAtStart, tAtEnd);
+    const PDFReal tMax = qMax(tAtStart, tAtEnd);
+
+    const bool isSingleFunction = m_functions.size() == 1;
+    std::vector<PDFReal> colorBuffer(m_colorSpace->getColorComponentCount(), 0.0);
+    auto getColor = [this, isSingleFunction, &colorBuffer](PDFReal t) -> PDFColor
+    {
+        if (isSingleFunction)
+        {
+            PDFFunction::FunctionResult result = m_functions.front()->apply(&t, &t + 1, colorBuffer.data(), colorBuffer.data() + colorBuffer.size());
+            if (!result)
+            {
+                throw PDFRendererException(RenderErrorType::Error, PDFTranslationContext::tr("Error occured during mesh creation of shading: %1").arg(result.errorMessage));
+            }
+        }
+        else
+        {
+            for (size_t i = 0, count = colorBuffer.size(); i < count; ++i)
+            {
+                PDFFunction::FunctionResult result = m_functions.front()->apply(&t, &t + 1, colorBuffer.data() + i, colorBuffer.data() + i + 1);
+                if (!result)
+                {
+                    throw PDFRendererException(RenderErrorType::Error, PDFTranslationContext::tr("Error occured during mesh creation of shading: %1").arg(result.errorMessage));
+                }
+            }
+        }
+
+        return PDFAbstractColorSpace::convertToColor(colorBuffer);
+    };
+
+    // Determine color of each coordinate
+    std::vector<std::pair<PDFReal, PDFColor>> coloredCoordinates;
+    coloredCoordinates.reserve(xCoords.size());
+
+    for (PDFReal x : xCoords)
+    {
+        if (x < p1m.x() - PDF_EPSILON && !m_extendStart)
+        {
+            // Move to the next coordinate, this is skipped
+            continue;
+        }
+
+        if (x > p2m.x() + PDF_EPSILON && !m_extendEnd)
+        {
+            // We are finished no more triangles will occur
+            break;
+        }
+
+        // Determine current parameter t
+        const PDFReal t = interpolate(x, p1m.x(), p2m.x(), tAtStart, tAtEnd);
+        const PDFReal tBounded = qBound(tMin, t, tMax);
+        const PDFColor color = getColor(tBounded);
+        coloredCoordinates.emplace_back(x, color);
+    }
+
+    // Filter coordinates according the meshing criteria
+    std::vector<std::pair<PDFReal, PDFColor>> filteredCoordinates;
+    filteredCoordinates.reserve(coloredCoordinates.size());
+
+    for (auto it = coloredCoordinates.cbegin(); it != coloredCoordinates.cend(); ++it)
+    {
+        // We will skip this coordinate, if both of meshing criteria have been met:
+        //  1) Color difference is small (lesser than tolerance)
+        //  2) Distance from previous and next point is less than preffered meshing resolution OR colors are equal
+
+        if (it != coloredCoordinates.cbegin() && std::next(it) != coloredCoordinates.cend())
+        {
+            auto itNext = std::next(it);
+
+            const std::pair<PDFReal, PDFColor>& prevItem = filteredCoordinates.back();
+            const std::pair<PDFReal, PDFColor>& currentItem = *it;
+            const std::pair<PDFReal, PDFColor>& nextItem = *itNext;
+
+            if (prevItem.second == currentItem.second && currentItem.second == nextItem.second)
+            {
+                // Colors are same, skip the test
+                continue;
+            }
+
+            if (PDFAbstractColorSpace::isColorEqual(prevItem.second, currentItem.second, settings.tolerance) &&
+                PDFAbstractColorSpace::isColorEqual(currentItem.second, nextItem.second, settings.tolerance) &&
+                PDFAbstractColorSpace::isColorEqual(prevItem.second, nextItem.second, settings.tolerance) &&
+                (nextItem.first - prevItem.first < settings.preferredMeshResolution))
+            {
+                continue;
+            }
+        }
+
+        filteredCoordinates.push_back(*it);
+    }
+
+    if (!filteredCoordinates.empty())
+    {
+        size_t vertexCount = filteredCoordinates.size() * 2;
+        size_t triangleCount = filteredCoordinates.size() * 2 - 2;
+
+        if (m_backgroundColor.isValid())
+        {
+            vertexCount += 8;
+            triangleCount += 4;
+        }
+        mesh.reserve(vertexCount, triangleCount);
+
+        PDFColor previousColor = filteredCoordinates.front().second;
+        uint32_t topLeft = mesh.addVertex(QPointF(filteredCoordinates.front().first, yt));
+        uint32_t bottomLeft = mesh.addVertex(QPointF(filteredCoordinates.front().first, yb));
+        for (auto it = std::next(filteredCoordinates.cbegin()); it != filteredCoordinates.cend(); ++it)
+        {
+            const std::pair<PDFReal, PDFColor>& item = *it;
+
+            uint32_t topRight = mesh.addVertex(QPointF(item.first, yt));
+            uint32_t bottomRight = mesh.addVertex(QPointF(item.first, yb));
+
+            PDFColor mixedColor = PDFAbstractColorSpace::mixColors(previousColor, item.second, 0.5);
+            QColor color = m_colorSpace->getColor(mixedColor);
+            mesh.addQuad(topLeft, topRight, bottomRight, bottomLeft, color.rgb());
+
+            topLeft = topRight;
+            bottomLeft = bottomRight;
+            previousColor = item.second;
+        }
+    }
+
+    // Create background color triangles
+
+    // Transform mesh to the device space coordinates
+    mesh.transform(p1p2LCS);
+
+    // Transform mesh from the device space coordinates to user space coordinates
+    Q_ASSERT(settings.userSpaceToDeviceSpaceMatrix.isInvertible());
+    QMatrix deviceSpaceToUserSpaceMatrix = settings.userSpaceToDeviceSpaceMatrix.inverted();
+    mesh.transform(deviceSpaceToUserSpaceMatrix);
+
+    // Create bounding path
+    if (m_boundingBox.isValid())
+    {
+        QPainterPath boundingPath;
+        boundingPath.addRect(m_boundingBox);
+        mesh.setBoundingPath(boundingPath);
+    }
+
+    return mesh;
+}
+
+void PDFMesh::paint(QPainter* painter) const
+{
+    if (m_triangles.empty())
+    {
+        return;
+    }
+
+    painter->save();
+    painter->setPen(Qt::NoPen);
+    painter->setRenderHint(QPainter::Antialiasing, true);
+
+    // Set the clipping area, if we have it
+    if (!m_boundingPath.isEmpty())
+    {
+        painter->setClipPath(m_boundingPath, Qt::IntersectClip);
+    }
+
+    QColor color;
+
+    // Draw all triangles
+    for (const Triangle& triangle : m_triangles)
+    {
+        if (color != triangle.color)
+        {
+            painter->setPen(QColor(triangle.color));
+            painter->setBrush(QBrush(triangle.color, Qt::SolidPattern));
+            color = triangle.color;
+        }
+
+        std::array<QPointF, 3> triangleCorners = { m_vertices[triangle.v1], m_vertices[triangle.v2], m_vertices[triangle.v3] };
+        painter->drawConvexPolygon(triangleCorners.data(), static_cast<int>(triangleCorners.size()));
+    }
+
+    painter->restore();
+}
+
+void PDFMesh::transform(const QMatrix& matrix)
+{
+    for (QPointF& vertex : m_vertices)
+    {
+        vertex = matrix.map(vertex);
+    }
+
+    m_boundingPath = matrix.map(m_boundingPath);
+}
+
+void PDFMeshQualitySettings::initDefaultResolution()
+{
+    // We will take 0.5% percent of device space meshing area as minimal resolution (it is ~1.5 mm for
+    // A4 page) and default resolution 4x number of that.
+
+    Q_ASSERT(deviceSpaceMeshingArea.isValid());
+    PDFReal size = qMax(deviceSpaceMeshingArea.width(), deviceSpaceMeshingArea.height());
+    minimalMeshResolution = size * 0.005;
+    preferredMeshResolution = minimalMeshResolution * 4;
+}
+
 }   // namespace pdf

PdfForQtLib/sources/pdfpattern.h

@@ -51,6 +51,87 @@ enum class ShadingType
     TensorProductPatchMesh = 7
 };
 
+struct PDFMeshQualitySettings
+{
+    /// Initializes default resolution
+    void initDefaultResolution();
+
+    /// Matrix, which transforms user space points (user space is target space of the shading)
+    /// to the device space of the paint device.
+    QMatrix userSpaceToDeviceSpaceMatrix;
+
+    /// Rectangle in device space coordinate system, onto which is area meshed.
+    QRectF deviceSpaceMeshingArea;
+
+    /// Preferred mesh resolution in device space pixels. Mesh will be created in this
+    /// resolution, if it is smooth enough (no jumps in colors occurs).
+    PDFReal preferredMeshResolution = 1.0;
+
+    /// Minimal mesh resolution in device space pixels. If jumps in colors occurs (jump
+    /// is two colors, that differ more than \p color tolerance), then mesh is meshed to
+    /// minimal mesh resolution.
+    PDFReal minimalMeshResolution = 1.0;
+
+    /// Color tolerance - 1% by default
+    PDFReal tolerance = 0.01;
+};
+
+/// Mesh consisting of triangles
+class PDFMesh
+{
+public:
+    explicit PDFMesh() = default;
+
+    struct Triangle
+    {
+        uint32_t v1 = 0;
+        uint32_t v2 = 0;
+        uint32_t v3 = 0;
+
+        QRgb color;
+    };
+
+    /// Adds vertex. Returns index of added vertex.
+    /// \param vertex Vertex to be added
+    /// \returns Index of the added vertex
+    inline uint32_t addVertex(const QPointF& vertex) { const size_t index = m_vertices.size(); m_vertices.emplace_back(vertex); return static_cast<uint32_t>(index); }
+
+    /// Adds triangle. Returns index of added triangle.
+    /// \param triangle Triangle to be added
+    /// \returns Index of the added vertex
+    inline uint32_t addTriangle(const Triangle& triangle) { const size_t index = m_triangles.size(); m_triangles.emplace_back(triangle); return static_cast<uint32_t>(index); }
+
+    /// Adds quad. Vertices are in clockwise order (so, we have edges v1-v2, v2-v3, v3-v4, v4-v1).
+    /// \param v1 First vertex (for example, topleft)
+    /// \param v2 Second vertex (for example, topright)
+    /// \param v3 Third vertex (for example, bottomright)
+    /// \param v4 Fourth vertex (for example, bottomleft)
+    /// \param color Color of the quad.
+    inline void addQuad(uint32_t v1, uint32_t v2, uint32_t v3, uint32_t v4, QRgb color) { addTriangle({v1, v2, v3, color}); addTriangle({ v1, v3, v4, color}); }
+
+    /// Paints the mesh on the painter
+    /// \param painter Painter, onto which is mesh drawn
+    void paint(QPainter* painter) const;
+
+    /// Transforms the mesh according to the matrix transform
+    /// \param matrix Matrix transform to be performed
+    void transform(const QMatrix& matrix);
+
+    /// Reserves memory for meshing - both number of vertices and triangles.
+    /// Use this function, if number of vertices and triangles is known.
+    /// \param vertexCount Vertex count
+    /// \param triangleCount Triangle count
+    void reserve(size_t vertexCount, size_t triangleCount) { m_vertices.reserve(vertexCount); m_triangles.reserve(triangleCount); }
+
+    const QPainterPath& getBoundingPath() const { return m_boundingPath; }
+    void setBoundingPath(const QPainterPath& path) { m_boundingPath = path; }
+
+private:
+    std::vector<QPointF> m_vertices;
+    std::vector<Triangle> m_triangles;
+    QPainterPath m_boundingPath;
+};
+
 /// Represents tiling/shading pattern
 class PDFPattern
 {
@@ -88,7 +169,7 @@ public:
                                               const PDFObject& patternGraphicState,
                                               bool ignoreBackgroundColor);
 
-private:
+protected:
     QRectF m_boundingBox;
     QMatrix m_matrix;
 };
@@ -102,6 +183,10 @@ public:
     virtual PatternType getType() const override;
     virtual ShadingType getShadingType() const = 0;
 
+    /// Creates a colored mesh using settings
+    /// \param settings Meshing settings
+    virtual PDFMesh createMesh(const PDFMeshQualitySettings& settings) const = 0;
+
     /// Returns patterns graphic state. This state must be applied before
     /// the shading pattern is painted to the target device.
     const PDFObject& getPatternGraphicState() const { return m_patternGraphicState; }
@@ -116,7 +201,7 @@ public:
     /// Returns true, if shading pattern should be anti-aliased
     bool isAntialiasing() const { return m_antiAlias; }
 
-private:
+protected:
     friend class PDFPattern;
 
     PDFObject m_patternGraphicState;
@@ -130,7 +215,7 @@ class PDFSingleDimensionShading : public PDFShadingPattern
 public:
     explicit PDFSingleDimensionShading() = default;
 
-private:
+protected:
     friend class PDFPattern;
 
     std::vector<PDFFunctionPtr> m_functions;
@@ -148,6 +233,7 @@ public:
     explicit PDFAxialShading() = default;
 
     virtual ShadingType getShadingType() const override;
+    virtual PDFMesh createMesh(const PDFMeshQualitySettings& settings) const override;
 
 private:
     friend class PDFPattern;