ImageUtils.cpp

#include "ImageUtils.h"

// Qt 4.6.2 includes a wonderfully optimized blur function in /src/gui/image/qpixmapfilter.cpp
// I'll just hook into their implementation here, instead of reinventing the wheel.
extern void qt_blurImage(QImage &blurImage, qreal radius, bool quality, int transposed = 0);

const qreal radiusScale = qreal(1.5);

// Copied from QPixmapBlurFilter::boundingRectFor(const QRectF &rect)
QRectF ImageUtils::blurredBoundingRectFor(const QRectF &rect, int radius)
{
	const qreal delta = radiusScale * radius + 1;
	return rect.adjusted(-delta, -delta, delta, delta);
}

QSizeF ImageUtils::blurredSizeFor(const QSizeF &size, int radius)
{
	const qreal delta = radiusScale * radius + 1;
	QSizeF newSize(size.width()  + delta,
	               size.height() + delta);

	return newSize;
}

// Modifies the input image, no copying
void ImageUtils::blurImage(QImage& image, int radius, bool highQuality)
{
	qt_blurImage(image, radius, highQuality);
}

// Blur the image according to the blur radius
// Based on exponential blur algorithm by Jani Huhtanen
// (maximum radius is set to 16)
QImage ImageUtils::blurred(const QImage& image, const QRect& /*rect*/, int radius)
{
	QImage copy = image.copy();
	qt_blurImage(copy, radius, false);
	return copy;
}

QImage ImageUtils::addDropShadow(QImage markerGroup, double shadowSize)
{
	// Add in drop shadow
	if(shadowSize > 0.0)
	{
// 		double shadowOffsetX = 0.0;
// 		double shadowOffsetY = 0.0;
		QColor shadowColor = Qt::black;

		// create temporary pixmap to hold a copy of the text
		QSizeF blurSize = blurredSizeFor(markerGroup.size(), (int)shadowSize);
		//qDebug() << "Blur size:"<<blurSize<<", doc:"<<doc.size()<<", shadowSize:"<<shadowSize;
		QImage tmpImage(blurSize.toSize(),QImage::Format_ARGB32_Premultiplied);
		memset(tmpImage.bits(),0,tmpImage.byteCount()); // init transparent

		// render the text
		QPainter tmpPainter(&tmpImage);

		tmpPainter.save();
		tmpPainter.translate(shadowSize, shadowSize);
		tmpPainter.drawImage(0,0,markerGroup);
		tmpPainter.restore();

		// blacken the image by applying a color to the copy using a QPainter::CompositionMode_DestinationIn operation.
		// This produces a homogeneously-colored pixmap.
		QRect rect = tmpImage.rect();
		tmpPainter.setCompositionMode(QPainter::CompositionMode_SourceIn);
		tmpPainter.fillRect(rect, shadowColor);
		tmpPainter.end();

		// blur the colored image
		blurImage(tmpImage, (int)shadowSize);

		// Render the original image back over the shadow
		tmpPainter.begin(&tmpImage);
		tmpPainter.save();
// 		tmpPainter.translate(shadowOffsetX - shadowSize,
// 				     shadowOffsetY - shadowSize);
		tmpPainter.translate(shadowSize, shadowSize);
		tmpPainter.drawImage(0,0,markerGroup);
		tmpPainter.restore();

		markerGroup = tmpImage;
	}

	return markerGroup;
}