Question

QT4如何模糊QPixmap图像？

我正在寻找以下其中一项：

Blur(pixmap); 
painter.Blur(); 
painter.Blur(rect);

这样做的最佳方式是什么？

Answer 1

1st）宣布外部QT例程：

QT_BEGIN_NAMESPACE
  extern Q_WIDGETS_EXPORT void qt_blurImage( QPainter *p, QImage &blurImage, qreal radius, bool quality, bool alphaOnly, int transposed = 0 );
QT_END_NAMESPACE

2）使用：

  extern QImage srcImg;//source image
  QPixmap pxDst( srcImg.size() );//blurred destination
  pxDst.fill( Qt::transparent );
  {
    QPainter painter( &pxDst );
    qt_blurImage( &painter, srcImg, 2, true, false );//blur radius: 2px
  }

Answer 2

方法1a：抓住原始位并自己动手。您需要充分熟悉位图和模糊算法以自己实现模糊。如果您想要那种精确度，那么就可以了。

QImage image = pixmap.toImage();
if (image.format() != QImage::Format_RGB32)
     image = image.convertToFormat(QImage::Format_RGB32);
uchar* bits = image.bits();
int rowBytes = image.bytesPerLine();
DoMyOwnBlurAlgorithm(bits, image.width(), image.height(), rowBytes);
return QPixmap::fromImage(image);

方法1b：谁需要原始位？您可以使用image.pixel（x，y）和image.setPixel（x，y，color）代替。这不会像1a那么快，但它应该更容易理解和编码。

QImage image = pixmap.toImage();
QImage output(image.width(), image.height(), image.format());
for (int y=0; y<image.height(); ++y)
   for (int x=0; x<image.width(); ++x)
      output.setPixel(getBlurredColor(image, x, y));
return output;

方法2：通过小部件或场景使用QGraphicsBlurEffect。这里的代码使用标签小部件：

QPixmap BlurAPixmap(const QPixmap& inPixmap)
{
    QLabel* label = new QLabel();
    label->setPixmap(inPixmap);
    label->setGraphicsEffect(new QGraphicsBlurEffect());
    QPixmap output(inPixmap.width(), inPixmap.height());
    QPainter painter(&output);
    label->render(&painter);
    return output;
}

根据需要调整。例如，我假设默认的图形模糊效果是可以接受的。我在我的项目中使用方法2。

Answer 3

看看这个：

#include <QtGui/QApplication>
#include <QImage>
#include <QPixmap>
#include <QLabel>

QImage blurred(const QImage& image, const QRect& rect, int radius, bool alphaOnly = false)
{
    int tab[] = { 14, 10, 8, 6, 5, 5, 4, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2 };
    int alpha = (radius < 1)  ? 16 : (radius > 17) ? 1 : tab[radius-1];

    QImage result = image.convertToFormat(QImage::Format_ARGB32_Premultiplied);
    int r1 = rect.top();
    int r2 = rect.bottom();
    int c1 = rect.left();
    int c2 = rect.right();

    int bpl = result.bytesPerLine();
    int rgba[4];
    unsigned char* p;

    int i1 = 0;
    int i2 = 3;

    if (alphaOnly)
        i1 = i2 = (QSysInfo::ByteOrder == QSysInfo::BigEndian ? 0 : 3);

    for (int col = c1; col <= c2; col++) {
        p = result.scanLine(r1) + col * 4;
        for (int i = i1; i <= i2; i++)
            rgba[i] = p[i] << 4;

        p += bpl;
        for (int j = r1; j < r2; j++, p += bpl)
            for (int i = i1; i <= i2; i++)
                p[i] = (rgba[i] += ((p[i] << 4) - rgba[i]) * alpha / 16) >> 4;
    }

    for (int row = r1; row <= r2; row++) {
        p = result.scanLine(row) + c1 * 4;
        for (int i = i1; i <= i2; i++)
            rgba[i] = p[i] << 4;

        p += 4;
        for (int j = c1; j < c2; j++, p += 4)
            for (int i = i1; i <= i2; i++)
                p[i] = (rgba[i] += ((p[i] << 4) - rgba[i]) * alpha / 16) >> 4;
    }

    for (int col = c1; col <= c2; col++) {
        p = result.scanLine(r2) + col * 4;
        for (int i = i1; i <= i2; i++)
            rgba[i] = p[i] << 4;

        p -= bpl;
        for (int j = r1; j < r2; j++, p -= bpl)
            for (int i = i1; i <= i2; i++)
                p[i] = (rgba[i] += ((p[i] << 4) - rgba[i]) * alpha / 16) >> 4;
    }

    for (int row = r1; row <= r2; row++) {
        p = result.scanLine(row) + c2 * 4;
        for (int i = i1; i <= i2; i++)
            rgba[i] = p[i] << 4;

        p -= 4;
        for (int j = c1; j < c2; j++, p -= 4)
            for (int i = i1; i <= i2; i++)
                p[i] = (rgba[i] += ((p[i] << 4) - rgba[i]) * alpha / 16) >> 4;
    }

    return result;
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QLabel label;
    QImage image("image.png");
    image =  blurred(image,image.rect(),10,false);
    label.setPixmap(QPixmap::fromImage(image));
    label.show();

    return a.exec();
}

Answer 4

让我们为这个话题做出贡献。从Qt 5.3开始，以下函数将帮助您将QGraphicsEffect应用于QImage（并且不会丢失alpha）

QImage applyEffectToImage(QImage src, QGraphicsEffect *effect, int extent = 0)
{
    if(src.isNull()) return QImage();   //No need to do anything else!
    if(!effect) return src;             //No need to do anything else!
    QGraphicsScene scene;
    QGraphicsPixmapItem item;
    item.setPixmap(QPixmap::fromImage(src));
    item.setGraphicsEffect(effect);
    scene.addItem(&item);
    QImage res(src.size()+QSize(extent*2, extent*2), QImage::Format_ARGB32);
    res.fill(Qt::transparent);
    QPainter ptr(&res);
    scene.render(&ptr, QRectF(), QRectF( -extent, -extent, src.width()+extent*2, src.height()+extent*2 ) );
    return res;
}

他们使用此功能来模糊您的图像非常简单：

QGraphicsBlurEffect *blur = new QGraphicsBlurEffect;
blur->setBlurRadius(8);
QImage source("://img1.png");
QImage result = applyEffectToImage(source, blur);
result.save("final.png");

当然，你不需要保存它，这只是一个有用的例子。你甚至可以放下一个阴影：

QGraphicsDropShadowEffect *e = new QGraphicsDropShadowEffect;
e->setColor(QColor(40,40,40,245));
e->setOffset(0,10);
e->setBlurRadius(50);
QImage p("://img3.png");
QImage res = applyEffectToImage(p, e, 40);

注意范围参数，它会在原始图像的所有边上添加extent个像素数，尤其适用于阴影和模糊不能被截断。

Answer 5

Gaussian blur是一种创建模糊效果的简单方法。

编辑：而且，我遇到了Qt的QGraphicsBlurEffect。在Qt 4.6中引入，似乎完全符合你的要求。

Answer 6

基于QT 5的@ПетърПетров答案添加python代码。

def applyEffectToImage(src, effect):
    scene = QGraphicsScene()
    item = QGraphicsPixmapItem()
    item.setPixmap(QPixmap.fromImage(src))
    item.setGraphicsEffect(effect)
    scene.addItem(item)
    res = QImage(src.size(), QImage.Format_ARGB32)
    res.fill(Qt.transparent)
    ptr = QPainter(res)
    scene.render(ptr, QRectF(), QRectF(0,0, src.width(), src.height()) )
    return res

blur = QGraphicsBlurEffect()
blur.setBlurRadius(8)
source = QImage(r"C:\Users\fran\Desktop\test.png")
result = applyEffectToImage(source, blur)
result.save(r"C:\Users\fran\Desktop\result.png")

QT4如何模糊QPixmap图像？

6 个答案: