Special Effects with Qt Graphics View

Special F/X with Graphics ViewAriya Hidayat 09/25/09

About Myself

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Open-source Developer

Ph.D in EE

Agenda

Four Dot Five– What you can do already

Four Dot Six– What you can (ab)use soon

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Goals

Provoke ideas!

Incite passion!

Engage creativity!

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A Word of Caution

With great power must come great responsibility.

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Spread the Love

All examples are available from...

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labs.qt.nokia.com

bit.ly/graphicsdojo

Qt 4.5

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Gradients

Transformation

Animation, Kinetic Scrolling

Composition Modes

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Linear Gradient

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Radial Gradient

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Gradients: Quick Recipe

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Applies to: QAbstractGraphicsShapeItem

QGraphicsEllipseItem, QGraphicsPathItem, QGraphicsPolygonItem, QGraphicsRectItem

or your own subclass(es).

Classes to use:– QLinearGradient– QRadialGradient– QConicalGradient

Linear Gradient: The Code

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QPoint start(0, 0);QPoint end(0, 20);

QLinearGradient g(start, end);g.setColorAt(0, Qt::white);g.setColorAt(1, Qt::black);

item->setBrush(g);

Radial Gradient: The Code

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QRadialGradient gr(100, 100, 100, 60, 60);gr.setColorAt(0.0, QColor(255, 255, 255, 191));gr.setColorAt(0.2, QColor(255, 255, 127, 191));gr.setColorAt(0.9, QColor(150, 150, 200, 63));p.setBrush(gr);p.drawEllipse(0, 0, 200, 200);

Shadow with Gradients

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magnifier

Shadow: The Code

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QRadialGradient g;g.setCenter(radius, radius);g.setFocalPoint(radius, radius);g.setRadius(radius);g.setColorAt(1.0, QColor(255, 255, 255, 0));g.setColorAt(0.5, QColor(128, 128, 128, 255));

QPainter mask(&maskPixmap);mask.setCompositionMode (QPainter::CompositionMode_Source);mask.setBrush(g);mask.drawRect(maskPixmap.rect());mask.setBrush(QColor(Qt::transparent));mask.drawEllipse(g.center(), radius-15, radius-15);mask.end();

Translucent Reflection

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Flip Vertically

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QImage::mirrored()

More Natural Look

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Linear gradient, on the alpha channel

Reflection: The Code

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QPoint start(0, 0);QPoint end(0, img.height());QLinearGradient gradient(start, end);gradient.setColorAt(0.5, Qt::black);gradient.setColorAt(0, Qt::white);

QImage mask = img;QPainter painter(&mask);painter.fillRect(img.rect(), gradient);painter.end();

QImage reflection = img.mirrored();reflection.setAlphaChannel(mask);

Opacity

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QPainter::setOpacity(...)

Transformation

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Scaling Rotation Perspective

Rotation

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transform.rotate(30, Qt::ZAxis)

Perspective Transformation: The Recipe

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transform.rotate(60, Qt::YAxis)

transform.rotate(60, Qt::XAxis)

Reflection & Transformation

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Timeline-based Animation

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acceleration

deacceleration

Linear Motion vs Non-linear Motion

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EaseInOutLinear

acceleration

deacceleration

Flick List (or Kinetic Scrolling)

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Using FlickCharm

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QGraphicsView canvas;

FlickCharm charm;charm.activateOn(&canvas);

Flick Charm & Event Filtering

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Steady

Pressed

Manual Scroll

Auto Scroll

Stop

Mouse release

Mouse move

Mouse release

Mouse press

Mousemove

Timer tick

Mouse press

Parallax Effect

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Composition Modes

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Colorize (or Tint Effect)

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Grayscale Conversion

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int pixels = img.width() * img.height();unsigned int *data = (unsigned int *)img.bits();for (int i = 0; i < pixels; ++i) { int val = qGray(data[i]); data[i] = qRgb(val, val, val);}

Overlay with Color

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QPainter painter(&resultImage);painter.drawImage(0, 0, grayscaled(image));painter.setCompositionMode (QPainter::CompositionMode_Overlay);painter.fillRect(resultImage.rect(), color);painter.end();

Glow Effect

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Night Mode

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Night Mode with Color Inversion

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QPainter p(this);p.setCompositionMode (QPainter::CompositionMode_Difference);p.fillRect(event->rect(), Qt::white);p.end();

red = 255 – red

green = 255 – green

blue = 255 - blue

A Friendly Advice: Fast Prototyping

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– avoid long edit-compile-debug cycle– use JavaScript, e.g. with Qt Script– use Python, e.g. with PyQt or PySide– use <insert your favorite dynamic language>

Qt 4.6

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Animation Framework

State Machine

Graphics Effects

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Animation Framework

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What People Want

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– (soft) drop shadow– blur– colorize– some other random stuff

Graphics F/X

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QGraphicsEffect

QGraphicsColorizeEffect

QGraphicsGrayscaleEffect

QGraphicsPixelizeEffect

QGraphicsBlurEffect

QGraphicsDropShadowEffect

QGraphicsOpacityEffect

Challenges

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– software vs hardware– good API

Software vs Hardware

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– software implementation• consistent and reliable• easy to test• cumbersome, (dog)slow

– hardware acceleration• blazing fast• custom effects are easy• silicon/driver dependent

API

One API to rule them all, ...

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Simple API

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– Effect is a QObject• might have property, e.g. Color• property change emits a signal• can be animated easily

– Effect applies to QGraphicsItem & QWidget– Custom effect? Subclass QGraphicsEffect

As Simple As...

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QGraphicsGrayscaleEffect *effect;effect = new QGraphicsGrayscaleEffect;item->setGraphicsEffect(effect);

Effect is applied to the itemand its children!

Grayscale Effect

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Grayscale Effect with Strength=0.8

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Colorize Effect

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Colorize Effect with Strength=0.8

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Pixelize Effect

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Blur Effect

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Drop Shadow Effect

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Lighting Example

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Blur Picker Example

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sharp

blurry

Fade Message Example

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Something will happen

Scale Effect

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Scale Effect Implementation

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void draw(QPainter *painter, QGraphicsEffectSource *source) {

QPixmap pixmap; pixmap = source->pixmap(Qt::DeviceCoordinates);

painter->save(); painter->setBrush(Qt::NoBrush); painter->setPen(Qt::red); painter->drawRect(pixmap.rect());

painter->scale(0.5, 0.5); painter->translate(pixmap.rect().bottomRight()/2); painter->drawPixmap(0, 0, pixmap);

painter->restore();}

Night Mode Effect

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Night Mode Effect Implementation

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void draw(QPainter *painter, QGraphicsEffectSource *source) {

QPixmap pixmap; pixmap = source->pixmap(Qt::DeviceCoordinates);

QPainter p(&pixmap); p.setCompositionMode (QPainter::CompositionMode_Difference); p.fillRect(pixmap.rect(), Qt::white); p.end(); painter->drawPixmap(0, 0, pixmap);}

Frame Effect

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Extending the Bounding Box

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QRectF boundingRectFor(const QRectF &rect) const { return rect.adjusted(-5, -5, 5, 5);}

item bounding box

“effective” bounding box

Frame Effect Implementation

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void draw(QPainter *painter, QGraphicsEffectSource *source) {

QPixmap pixmap; pixmap = source->pixmap(Qt::DeviceCoordinates); QRectF bound = boundingRectFor(pixmap.rect());

painter->save(); painter->setPen(Qt::NoPen); painter->setBrush(Qt::green); painter->drawRoundedRect(bound, 15, 15); painter->drawPixmap(0, 0, pixmap); painter->restore();}

Reflection Effect

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Enlarging the Bounding Box (Again)

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QRectF boundingRectFor(const QRectF &rect) const { return rect.adjusted(0, 0, 0, rect.height());}

item bounding box

“effective” bounding box

Reflection Effect Implementation

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void draw(QPainter *painter, QGraphicsEffectSource *source) {

QPixmap pixmap; pixmap = source->pixmap(Qt::DeviceCoordinates);

painter->save(); painter->drawPixmap(0, 0, pixmap); painter->setOpacity(0.2); painter->scale(1, -1); painter->translate(0, -pixmap.height()); painter->drawPixmap(0, 0, pixmap); painter->restore();}

Qt 4.7?

Future?

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Declarative UI

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Further Directions

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– Optimization!– Composite effects– Geometry deformation– Morphing– More physics: force, gravity, ...– Bitmap vs vector

Genie Effect

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Deformation

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Underwater Effect

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Thank You!

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That's all, folks...

Bleeding-Edge

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labs.qt.nokia.com

bit.ly/graphicsdojo