QGIS API Documentation  2.18.3-Las Palmas (77b8c3d)
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QgsPaintEffect Class Referenceabstract

Base class for visual effects which can be applied to QPicture drawings. More...

#include <qgspainteffect.h>

Inheritance diagram for QgsPaintEffect:
Inheritance graph
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Public Types

enum  DrawMode { Modifier, Render, ModifyAndRender }
 Drawing modes for effects. More...
 

Public Member Functions

 QgsPaintEffect ()
 
 QgsPaintEffect (const QgsPaintEffect &other)
 
virtual ~QgsPaintEffect ()
 
virtual void begin (QgsRenderContext &context)
 Begins intercepting paint operations to a render context. More...
 
virtual QgsPaintEffectclone () const =0
 Duplicates an effect by creating a deep copy of the effect. More...
 
DrawMode drawMode () const
 Returns the draw mode for the effect. More...
 
bool enabled () const
 Returns whether the effect is enabled. More...
 
virtual void end (QgsRenderContext &context)
 Ends interception of paint operations to a render context, and draws the result to the render context after being modified by the effect. More...
 
virtual QgsStringMap properties () const =0
 Returns the properties describing the paint effect encoded in a string format. More...
 
virtual void readProperties (const QgsStringMap &props)=0
 Reads a string map of an effect's properties and restores the effect to the state described by the properties map. More...
 
virtual bool readProperties (const QDomElement &element)
 Restores the effect to the state described by a DOM element. More...
 
virtual void render (QPicture &picture, QgsRenderContext &context)
 Renders a picture using the effect. More...
 
virtual bool saveProperties (QDomDocument &doc, QDomElement &element) const
 Saves the current state of the effect to a DOM element. More...
 
void setDrawMode (const DrawMode drawMode)
 Sets the draw mode for the effect. More...
 
void setEnabled (const bool enabled)
 Sets whether the effect is enabled. More...
 
virtual QString type () const =0
 Returns the effect type. More...
 

Protected Member Functions

virtual QRectF boundingRect (const QRectF &rect, const QgsRenderContext &context) const
 Returns the bounding rect required for drawing the effect. More...
 
virtual void draw (QgsRenderContext &context)=0
 Handles drawing of the effect's result on to the specified render context. More...
 
void drawSource (QPainter &painter)
 Draws the source QPicture onto the specified painter. More...
 
void fixQPictureDpi (QPainter *painter) const
 Applies a workaround to a QPainter to avoid an issue with incorrect scaling when drawing QPictures. More...
 
QPointF imageOffset (const QgsRenderContext &context) const
 Returns the offset which should be used when drawing the source image on to a destination render context. More...
 
const QPicturesource () const
 Returns the source QPicture. More...
 
QImagesourceAsImage (QgsRenderContext &context)
 Returns the source QPicture rendered to a new QImage. More...
 

Protected Attributes

DrawMode mDrawMode
 
bool mEnabled
 
bool requiresQPainterDpiFix
 

Friends

class QgsEffectStack
 

Detailed Description

Base class for visual effects which can be applied to QPicture drawings.

QgsPaintEffect objects can be used to modify QPicture drawings prior to rendering them with a QPainter operation. There are two methods for drawing using an effect, either drawing a picture directly, or by intercepting drawing operations to a render context.

To directly draw a picture, use the render method with a source QPicture and destination render context.

Intercepting drawing operations to a render context is achieved by first calling the begin method, passing a render context. Any drawing operations performed on the render context will not directly affect the context's paint device. When the drawing operations have been completed, call the end method. This will perform the paint effect on the intercepted drawing operations and render the result to the render context's paint device.

See also
QgsPaintEffectRegistry
Note
Added in version 2.9

Definition at line 49 of file qgspainteffect.h.

Member Enumeration Documentation

Drawing modes for effects.

These modes are used only when effects are drawn as part of an effects stack

See also
QgsEffectStack
Enumerator
Modifier 

the result of the effect is not rendered, but is passed on to following effects in the stack

Render 

the result of the effect is rendered on the destination, but does not affect subsequent effects in the stack

ModifyAndRender 

the result of the effect is both rendered and passed on to subsequent effects in the stack

Definition at line 58 of file qgspainteffect.h.

Constructor & Destructor Documentation

QgsPaintEffect::QgsPaintEffect ( )

Definition at line 26 of file qgspainteffect.cpp.

QgsPaintEffect::QgsPaintEffect ( const QgsPaintEffect other)

Definition at line 40 of file qgspainteffect.cpp.

QgsPaintEffect::~QgsPaintEffect ( )
virtual

Definition at line 54 of file qgspainteffect.cpp.

Member Function Documentation

void QgsPaintEffect::begin ( QgsRenderContext context)
virtual

Begins intercepting paint operations to a render context.

When the corresponding end member is called all intercepted paint operations will be drawn to the render context after being modified by the effect.

Parameters
contextdestination render context
See also
end
render

Definition at line 137 of file qgspainteffect.cpp.

QRectF QgsPaintEffect::boundingRect ( const QRectF rect,
const QgsRenderContext context 
) const
protectedvirtual

Returns the bounding rect required for drawing the effect.

This method can be used to expand the bounding rect of a source picture to account for offset or blurring effects.

Parameters
rectoriginal source bounding rect
contextdestination render context
Returns
modified bounding rect
See also
sourceAsImage

Reimplemented in QgsTransformEffect, QgsGlowEffect, QgsShadowEffect, and QgsBlurEffect.

Definition at line 223 of file qgspainteffect.cpp.

virtual QgsPaintEffect* QgsPaintEffect::clone ( ) const
pure virtual

Duplicates an effect by creating a deep copy of the effect.

Returns
clone of paint effect

Implemented in QgsInnerGlowEffect, QgsDrawSourceEffect, QgsOuterGlowEffect, QgsInnerShadowEffect, QgsDropShadowEffect, QgsEffectStack, QgsBlurEffect, QgsTransformEffect, and QgsColorEffect.

virtual void QgsPaintEffect::draw ( QgsRenderContext context)
protectedpure virtual

Handles drawing of the effect's result on to the specified render context.

Derived classes must reimplement this method to apply any transformations to the source QPicture and draw the result using the context's painter.

Parameters
contextdestination render context
See also
drawSource

Implemented in QgsDrawSourceEffect, QgsTransformEffect, QgsGlowEffect, QgsColorEffect, QgsShadowEffect, QgsEffectStack, and QgsBlurEffect.

DrawMode QgsPaintEffect::drawMode ( ) const
inline

Returns the draw mode for the effect.

This property only has an effect if the paint effect is used in a QgsEffectStack

Returns
draw mode for effect
See also
setDrawMode

Definition at line 151 of file qgspainteffect.h.

void QgsPaintEffect::drawSource ( QPainter painter)
protected

Draws the source QPicture onto the specified painter.

Handles scaling of the picture to account for the destination painter's DPI.

Parameters
painterdestination painter
See also
source
sourceAsImage

Definition at line 178 of file qgspainteffect.cpp.

bool QgsPaintEffect::enabled ( ) const
inline

Returns whether the effect is enabled.

Returns
true if effect is enabled
See also
setEnabled

Definition at line 138 of file qgspainteffect.h.

void QgsPaintEffect::end ( QgsRenderContext context)
virtual

Ends interception of paint operations to a render context, and draws the result to the render context after being modified by the effect.

Parameters
contextdestination render context
See also
begin

Definition at line 152 of file qgspainteffect.cpp.

void QgsPaintEffect::fixQPictureDpi ( QPainter painter) const
protected

Applies a workaround to a QPainter to avoid an issue with incorrect scaling when drawing QPictures.

This may need to be called by derived classes prior to rendering results onto a painter.

Parameters
painterdestination painter

Definition at line 229 of file qgspainteffect.cpp.

QPointF QgsPaintEffect::imageOffset ( const QgsRenderContext context) const
protected

Returns the offset which should be used when drawing the source image on to a destination render context.

Parameters
contextdestination render context
Returns
point offset for image top left corner
See also
sourceAsImage

Definition at line 218 of file qgspainteffect.cpp.

virtual QgsStringMap QgsPaintEffect::properties ( ) const
pure virtual

Returns the properties describing the paint effect encoded in a string format.

Returns
string map of properties, in the form property key, value
See also
readProperties
saveProperties

Implemented in QgsDrawSourceEffect, QgsEffectStack, QgsBlurEffect, QgsGlowEffect, QgsTransformEffect, QgsColorEffect, and QgsShadowEffect.

virtual void QgsPaintEffect::readProperties ( const QgsStringMap props)
pure virtual

Reads a string map of an effect's properties and restores the effect to the state described by the properties map.

Parameters
propseffect properties encoded in a string map
See also
properties

Implemented in QgsDrawSourceEffect, QgsEffectStack, QgsBlurEffect, QgsGlowEffect, QgsTransformEffect, QgsColorEffect, and QgsShadowEffect.

bool QgsPaintEffect::readProperties ( const QDomElement element)
virtual

Restores the effect to the state described by a DOM element.

Parameters
elementDOM element describing an effect's state
Returns
true if read was successful
See also
saveProperties

Reimplemented in QgsEffectStack.

Definition at line 97 of file qgspainteffect.cpp.

void QgsPaintEffect::render ( QPicture picture,
QgsRenderContext context 
)
virtual

Renders a picture using the effect.

Parameters
picturesource QPicture to render
contextdestination render context
See also
begin

Definition at line 127 of file qgspainteffect.cpp.

bool QgsPaintEffect::saveProperties ( QDomDocument doc,
QDomElement element 
) const
virtual

Saves the current state of the effect to a DOM element.

The default behaviour is to save the properties string map returned by properties.

Parameters
docdestination DOM document
elementdestination DOM element
Returns
true if save was successful
See also
readProperties

Reimplemented in QgsEffectStack.

Definition at line 74 of file qgspainteffect.cpp.

void QgsPaintEffect::setDrawMode ( const DrawMode  drawMode)

Sets the draw mode for the effect.

This property only has an effect if the paint effect is used in a QgsEffectStack

Parameters
drawModedraw mode for effect
See also
drawMode

Definition at line 69 of file qgspainteffect.cpp.

void QgsPaintEffect::setEnabled ( const bool  enabled)

Sets whether the effect is enabled.

Parameters
enabledset to false to disable the effect
See also
enabled

Definition at line 64 of file qgspainteffect.cpp.

const QPicture* QgsPaintEffect::source ( ) const
inlineprotected

Returns the source QPicture.

The draw member can utilise this when drawing the effect.

Returns
source QPicture
See also
drawSource
sourceAsImage

Definition at line 188 of file qgspainteffect.h.

QImage * QgsPaintEffect::sourceAsImage ( QgsRenderContext context)
protected

Returns the source QPicture rendered to a new QImage.

The draw member can utilise this when drawing the effect. The image will be padded or cropped from the original source QPicture by the results of the boundingRect method. The result is cached to speed up subsequent calls to sourceAsImage.

Returns
source QPicture rendered to an image
See also
drawSource
source
imageOffset
boundingRect

Definition at line 193 of file qgspainteffect.cpp.

virtual QString QgsPaintEffect::type ( ) const
pure virtual

Returns the effect type.

Returns
unique string representation of the effect type

Implemented in QgsInnerGlowEffect, QgsDrawSourceEffect, QgsOuterGlowEffect, QgsInnerShadowEffect, QgsDropShadowEffect, QgsEffectStack, QgsBlurEffect, QgsTransformEffect, and QgsColorEffect.

Friends And Related Function Documentation

friend class QgsEffectStack
friend

Definition at line 239 of file qgspainteffect.h.

Member Data Documentation

DrawMode QgsPaintEffect::mDrawMode
protected

Definition at line 163 of file qgspainteffect.h.

bool QgsPaintEffect::mEnabled
protected

Definition at line 162 of file qgspainteffect.h.

bool QgsPaintEffect::requiresQPainterDpiFix
protected

Definition at line 164 of file qgspainteffect.h.


The documentation for this class was generated from the following files: