Copy A non-Rectangular Image

[Parvat]

hi

I am able to crop image by using the copy() function by copying image from rectItem that i have drawn,but when i rotate image to 20 degree or any degree and now i want to crop that rotate rect Image, how can i copy a nonRectangular Image
Help me guys .

[Santosh Reddy]

The rotated image can be copied the same way as not rotated image, what is problem it doing so?

[Parvat]

i did try to copy the roated image from the Rect but u see as soon as i rotate the Rect the Rect is no longer a Rectangle it becomes a Ploygon so now how can i copy that because copy function only take Rect Paramter.....so how ll i copy that new Rect(thats now a polygon)...hope U got what i mean to say.


or is there any alternate way to copy or crop from any shape beside only Rect

[ChrisW67]

Rotated or not, a rectangle is still a rectangle.

QImage::copy() can only copy a rectangle that is aligned with the sides of the image. If you want to copy a rectangular area that is rotated some number of degrees from horizontal then you need to rotate the QImage in the opposite direction and take a horizontal rectangular copy() from that image.

Of course, if you have the content of the rectangle before you rotated it then, in an ideal world, that is what it contains after you rotate it also.

[Parvat]

If you want to copy a rectangular area that is rotated some number of degrees from horizontal then you need to rotate the QImage in the opposite direction and take a horizontal rectangular copy() from that image.

.

Sorry Chris but i m still not getting it .
this is My code plzz check it .

//Image loading is Done.
//File Crop Code
 
void FileCropper::onFileCrop()
{
    myLeft=ui->myLeftSpinBox->value();
    myRight=ui->myRightSpinBox->value();
    myTop=ui->myTopSpinBox->value();
    myBottom=ui->myBottomSpinBox->value();
    QPixmap pixmap = myBeforePixItem->pixmap();
 
    QRectF newRect = myRectItem->rect();
    QPointF point = myRectItem->scenePos();
    float x = point.x();
    float y = point.y();
    QRectF moveRect( x + newRect.left() , y + newRect.top() , newRect.width(), newRect.height() );
    qDebug()<<"X:"<<x;
    qDebug()<<"Y:"<<y;
    QPixmap newImage = pixmap.copy( moveRect.toRect() );
    myAfterScene.setSceneRect( 0, 0, newRect.width(), newRect.height());
    ui->myAfterGraphicsVew->fitInView(myAfterScene.sceneRect(),Qt::KeepAspectRatio);
    ui->myAfterGraphicsVew->centerOn(newRect.width()/2,newRect.height()/2);
    myAfterPixItem->setPixmap( newImage );
}
//my Rect Code
 
void FileCropper::onChange()
{
    myLeft=ui->myLeftSpinBox->value();
    myRight=ui->myRightSpinBox->value();
    myTop=ui->myTopSpinBox->value();
    myBottom=ui->myBottomSpinBox->value();
    QPixmap pixmap = myBeforePixItem->pixmap();
    QRectF newRect( myLeft, myTop, pixmap.width() - myLeft -myRight, pixmap.height() - myTop -myBottom );
    myRectItem->setRect( newRect );
}
//Rotate Code
void FileCropper::onRotate(int val)
{
    QRectF rotateRect(0,0,myBeforePixItem->pixmap().width(),myBeforePixItem->pixmap().height());
    QTransform t;
    t.translate(rotateRect.center().x(),rotateRect.center().y());
    t.rotate(val);
    t.translate(-rotateRect.center().x(),-rotateRect.center().y());
    myRectItem->setTransform(t,false);
}

//Image loading is Done.
//File Crop Code

void FileCropper::onFileCrop()
{
    myLeft=ui->myLeftSpinBox->value();
    myRight=ui->myRightSpinBox->value();
    myTop=ui->myTopSpinBox->value();
    myBottom=ui->myBottomSpinBox->value();
    QPixmap pixmap = myBeforePixItem->pixmap();
   
    QRectF newRect = myRectItem->rect();
    QPointF point = myRectItem->scenePos();
    float x = point.x();
    float y = point.y();
    QRectF moveRect( x + newRect.left() , y + newRect.top() , newRect.width(), newRect.height() );
    qDebug()<<"X:"<<x;
    qDebug()<<"Y:"<<y;
    QPixmap newImage = pixmap.copy( moveRect.toRect() );
    myAfterScene.setSceneRect( 0, 0, newRect.width(), newRect.height());
    ui->myAfterGraphicsVew->fitInView(myAfterScene.sceneRect(),Qt::KeepAspectRatio);
    ui->myAfterGraphicsVew->centerOn(newRect.width()/2,newRect.height()/2);
    myAfterPixItem->setPixmap( newImage );
}
//my Rect Code

void FileCropper::onChange()
{
    myLeft=ui->myLeftSpinBox->value();
    myRight=ui->myRightSpinBox->value();
    myTop=ui->myTopSpinBox->value();
    myBottom=ui->myBottomSpinBox->value();
    QPixmap pixmap = myBeforePixItem->pixmap();
    QRectF newRect( myLeft, myTop, pixmap.width() - myLeft -myRight, pixmap.height() - myTop -myBottom );
    myRectItem->setRect( newRect );
}
//Rotate Code
void FileCropper::onRotate(int val)
{
    QRectF rotateRect(0,0,myBeforePixItem->pixmap().width(),myBeforePixItem->pixmap().height());
    QTransform t;
    t.translate(rotateRect.center().x(),rotateRect.center().y());
    t.rotate(val);
    t.translate(-rotateRect.center().x(),-rotateRect.center().y());
    myRectItem->setTransform(t,false);
}

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[ChrisW67]

You started off wanting to copy a rectangular area, now you want to crop an image.

The resulting image must be rectangular. What exactly do you want to occur to the areas outside the rotated rectangle? What size should the resulting image be; the same size as the original, or the minimum size to hold the rotated rectangle?

Here is one approach to extract an arbitrary area:

#include <QtGui>
 
int main(int argc, char **argv)
{
    QApplication app(argc, argv);
 
    // http://en.wikipedia.org/wiki/File:Lenna.png
    QPixmap source("Lenna.png");
 
    // My desired rectangle
    QRect area(150, 150, 300, 50);
    QTransform transform;
    transform.translate(area.center().x(), area.center().y());
    transform.rotate(45);
    transform.translate(-area.center().x(), -area.center().y());
 
    QBitmap mask(source.size());
    mask.fill(Qt::color1);
    QPainter p(&mask);
    p.setPen(Qt::color0);
    p.setBrush(Qt::color0);
    p.setTransform(transform);
    p.drawRect(area);
    p.end();
 
    QPixmap dest(source);
    dest.setAlphaChannel(mask);
 
    QLabel before;
    before.setPixmap(source);
    QLabel after;
    after.setPixmap(dest);
 
    before.show();
    after.show();
 
    return app.exec();
}

#include <QtGui>

int main(int argc, char **argv)
{
    QApplication app(argc, argv);

    // http://en.wikipedia.org/wiki/File:Lenna.png
    QPixmap source("Lenna.png");

    // My desired rectangle
    QRect area(150, 150, 300, 50);
    QTransform transform;
    transform.translate(area.center().x(), area.center().y());
    transform.rotate(45);
    transform.translate(-area.center().x(), -area.center().y());

    QBitmap mask(source.size());
    mask.fill(Qt::color1);
    QPainter p(&mask);
    p.setPen(Qt::color0);
    p.setBrush(Qt::color0);
    p.setTransform(transform);
    p.drawRect(area);
    p.end();

    QPixmap dest(source);
    dest.setAlphaChannel(mask);

    QLabel before;
    before.setPixmap(source);
    QLabel after;
    after.setPixmap(dest);

    before.show();
    after.show();

    return app.exec();
}

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[Parvat]

i have send you my app image where in 1st image it does the cropping(copying ) of image perfectly but in 2 image i have rotate the rectangle and when i crop the result is in 2nd Image .

i want to send my exe file how can i send u so that u can check what i meant to say?
1.jpg2.jpg1.jpg2.jpg
thanks for the approach .

[ChrisW67]

i want to send my exe file how can i send u so that u can check what i meant to say?

Don't. I won't run it even if you gave me one that would run on my system, and I suspect no-one else will either. There are obvious reasons for banning executables.

It is not the forum's job to discern your requirements or test your software. If you want to explain your requirement then do so in English, with the aid of pictures (screen shots or mock-ups). You can easily upload images to this forum. Perhaps then we will understand exactly what it is you want.

[Parvat]

k sorry for that i got it i have uploaded images .....

[ChrisW67]

I still don't know what you expected to see.
For this input and selected rectangular area:
No0.jpg
Did you expect this:
No1.jpg
or this:
No2.jpg
(black areas transparent) or something else?

[Parvat]

I still don't know what you expected to see.
For this input and selected rectangular area:
No0.jpg
Did you expect this:
No1.jpg
or this:
No2.jpg
(black areas transparent) or something else?

Finally you got it what i mean to say
For the image you gave
i expected 1st output .
No1.jpg
back area Transparent

Thanks Chris for understanding my query.

[ChrisW67]

Then my previous example code is exactly what you need.
Construct a rectangle of the specified size.
Construct a transform to rotate and shift it to the specified coordinates.
Make a mask using a transformed painter
Apply the mask as the alpha channel of a copy of the image.
Profit.

[Parvat]

Thanks .finally got it .