QImage Rotation and Translation & Invert Specific Colors

**2lights** · 14th August 2013, 09:19

Good Day,

Part 1 of 2
Im superimposing 2 images(Overlaying images, with the 2nd image having a 50% opacity)

Now I have a rotation angle, a Row Offset & Column Offset Value.

When I rotate the 2nd image... it works
When a call the TRANSLATE function nothing happens!

Overlay Images Function:

Qt Code:

Switch view

primaryImage.load(imageFileName1);
 
     secondaryImage.load(imageFileName2);
     secondaryImage.invertPixels(); //Inverting Grayscale Image
 
     QTransform rotating;
     rotating.rotate(RotationAngle);
     secondaryImage = secondaryImage.transformed(rotating); // Works
     QTransform translating;
     translating.translate(RowOffset, ColOffset);
     secondaryImage = secondaryImage.transformed(translating); // Does not work
 
     paintScreen = true;
     update();

primaryImage.load(imageFileName1);

     secondaryImage.load(imageFileName2);
     secondaryImage.invertPixels(); //Inverting Grayscale Image

     QTransform rotating;
     rotating.rotate(RotationAngle);
     secondaryImage = secondaryImage.transformed(rotating); // Works
     QTransform translating;
     translating.translate(RowOffset, ColOffset);
     secondaryImage = secondaryImage.transformed(translating); // Does not work

     paintScreen = true;
     update();

To copy to clipboard, switch view to plain text mode

this is what I got:

Qt Code:

Switch view

//Paint Function
    if(paintScreen = true){
 
    //Repaint Primary Image
    painter.drawImage(QPoint(0, 0), primaryImage);
    painter.setOpacity(0.5);// drawn at n% opacity
    painter.drawImage(QPoint(0, 0), secondaryImage); }

//Paint Function
    if(paintScreen = true){

    //Repaint Primary Image
    painter.drawImage(QPoint(0, 0), primaryImage);
    painter.setOpacity(0.5);// drawn at n% opacity
    painter.drawImage(QPoint(0, 0), secondaryImage); }

To copy to clipboard, switch view to plain text mode

Ideas Please
Solutions welcome

Part 2 of 2
Also Instead of inverting colors of 2nd image(grayscale)
Is there a way to convert the whole image into like a "Red Scale" or any other color of different shades

Solution
Kind Regards

**karankumar1609** · 14th August 2013, 10:09

reference from THIS

Qt Code:

Switch view

#include <QtGui>
 
    int main(int argc, char** argv)
    {
        QApplication app(argc, argv);
        QPixmap pixmap("logo.png");
        QImage image = pixmap.toImage();
        QRgb col;
        int gray;
        int width = pixmap.width();
        int height = pixmap.height();
        for (int i = 0; i < width; ++i)
        {
            for (int j = 0; j < height; ++j)
            {
                col = image.pixel(i, j);
                gray = qGray(col);
                image.setPixel(i, j, qRgb(gray, gray, gray));
            }
        }
        pixmap = pixmap.fromImage(image);
        QLabel label;
        label.setPixmap(pixmap);
        label.show();
        return app.exec();
    }

#include <QtGui>
     
    int main(int argc, char** argv)
    {
        QApplication app(argc, argv);
        QPixmap pixmap("logo.png");
        QImage image = pixmap.toImage();
        QRgb col;
        int gray;
        int width = pixmap.width();
        int height = pixmap.height();
        for (int i = 0; i < width; ++i)
        {
            for (int j = 0; j < height; ++j)
            {
                col = image.pixel(i, j);
                gray = qGray(col);
                image.setPixel(i, j, qRgb(gray, gray, gray));
            }
        }
        pixmap = pixmap.fromImage(image);
        QLabel label;
        label.setPixmap(pixmap);
        label.show();
        return app.exec();
    }

To copy to clipboard, switch view to plain text mode

following example convert the image into an gray scale image.
HERE:

gray = qGray(col);

convert the QRgb color set into a gray color.
You can use QRed, QBlue etc. according to your need.

**2lights** · 14th August 2013, 10:29

Part 1 of 2
Any ideas

Part 2 of 2
Tried it, this is what i get
No compile error, But nothing happens no change to color
Though
I get this debug output err:
QImage:: pixel: coordinate (320,478) out of range
QImage:: setPixel: coordinate (320,478) out of range
QImage:: pixel: coordinate (320,479) out of range
...

Qt Code:

Switch view

void Compare::OverLayImages()
 {
     primaryImage.load(imageFileName1);
 
     QRgb colour;
     int newCol;
     int width = primaryImage.width();
     int height = primaryImage.height();
 
     for(int i = 0; i <= width; ++i)
        {
            for (int j = 0; j <= height; ++j)
            {
                colour = primaryImage.pixel(i, j);
                newCol = qRed(colour);
                primaryImage.setPixel(i, j, qRgb(newCol, newCol, newCol));
            }
        }

void Compare::OverLayImages()
 {
     primaryImage.load(imageFileName1);

     QRgb colour;
     int newCol;
     int width = primaryImage.width();
     int height = primaryImage.height();

     for(int i = 0; i <= width; ++i)
        {
            for (int j = 0; j <= height; ++j)
            {
                colour = primaryImage.pixel(i, j);
                newCol = qRed(colour);
                primaryImage.setPixel(i, j, qRgb(newCol, newCol, newCol));
            }
        }

To copy to clipboard, switch view to plain text mode

**karankumar1609** · 14th August 2013, 10:51

for(int i = 0; i <= width; ++i)

for (int j = 0; j <= height; ++j)

Loop should be i < width, and j < height.

mentioned code should work. may be you are doing it differently.
Where do you use this primaryImage?

Have you tried Image Composition Example

**2lights** · 14th August 2013, 11:38

i < width, and j < height.
Same problem
QImage::setPixel: Index -16645630 out of range
QImage::setPixel: Index -16645630 out of range
....
Nothing happens

Part of my program requires me to paint the image in a label
Could that be the problem... I doubt it thiugh because the editing takes place before the paint function is called

paint function

Qt Code:

Switch view

painter.setWindow(QRect(0,0,totalWidth,totalHeight));
    update();
 
    //Repaint Primary Image
    painter.drawImage(QPoint(0, 0), primaryImage);

painter.setWindow(QRect(0,0,totalWidth,totalHeight));
    update();

    //Repaint Primary Image
    painter.drawImage(QPoint(0, 0), primaryImage);

To copy to clipboard, switch view to plain text mode

painting no problem...
color is the issue!

& Any ideas on the translation of image

**wysota** · 14th August 2013, 11:54

Originally Posted by 2lights

When a call the TRANSLATE function nothing happens!

That's correct, translating an image will have no effect. The result of calling transformed() is a new image that can encompass the whole original image after applying a transformation to it. When rotating an image, the new resulting image will be larger and will contain all the contents or the original image. When translating, the new image will have the same size as the original one and will contain the whole original image -- which is identical to the original image.

this is what I got:

Qt Code:

Switch view

//Paint Function
    if(paintScreen = true){
 
    //Repaint Primary Image
    painter.drawImage(QPoint(0, 0), primaryImage);
    painter.setOpacity(0.5);// drawn at n% opacity
    painter.drawImage(QPoint(0, 0), secondaryImage); }

//Paint Function
    if(paintScreen = true){

    //Repaint Primary Image
    painter.drawImage(QPoint(0, 0), primaryImage);
    painter.setOpacity(0.5);// drawn at n% opacity
    painter.drawImage(QPoint(0, 0), secondaryImage); }

To copy to clipboard, switch view to plain text mode

That's very easy:

Qt Code:

Switch view

painter.drawImage(0, 0, primaryImage);
painter.setOpacity(0.5);
painter.drawImage(colShift, rowShift, secondaryImage);

painter.drawImage(0, 0, primaryImage);
painter.setOpacity(0.5);
painter.drawImage(colShift, rowShift, secondaryImage);

To copy to clipboard, switch view to plain text mode

You can do the same with rotation, by the way:

Qt Code:

Switch view

painter.drawImage(..., ..., primaryImage);
painter.save();
painter.translate(primaryImage.width()/2, primaryImage.height()/2);
painter.rotate(45);
painter.drawImage(..., ..., secondaryImage);
painter.restore();

painter.drawImage(..., ..., primaryImage);
painter.save();
painter.translate(primaryImage.width()/2, primaryImage.height()/2);
painter.rotate(45);
painter.drawImage(..., ..., secondaryImage);
painter.restore();

To copy to clipboard, switch view to plain text mode

Is there a way to convert the whole image into like a "Red Scale" or any other color of different shades

Sure, iterate over all pixels and change their color in any way you want.

**karankumar1609** · 14th August 2013, 12:03

You require to set a result image on QLabel..
The better way to do this, is have a result image and paint on it (Outside the paint event).
After loading of primaryImage and secondaryImage you can do your calculations on images and create a result image

Qt Code:

Switch view

void ImageComposer::recalculateResult()
{
    QPainter::CompositionMode mode = currentMode();
 
    QPainter painter(&resultImage);
    painter.setCompositionMode(QPainter::CompositionMode_Source);
    painter.fillRect(resultImage.rect(), Qt::transparent);
    painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
    painter.drawImage(0, 0, destinationImage);
    painter.setCompositionMode(mode);
    painter.drawImage(0, 0, sourceImage);
    painter.setCompositionMode(QPainter::CompositionMode_DestinationOver);
    painter.fillRect(resultImage.rect(), Qt::white);
    painter.end();
 
    resultLabel->setPixmap(QPixmap::fromImage(resultImage));
}

void ImageComposer::recalculateResult()
{
    QPainter::CompositionMode mode = currentMode();

    QPainter painter(&resultImage);
    painter.setCompositionMode(QPainter::CompositionMode_Source);
    painter.fillRect(resultImage.rect(), Qt::transparent);
    painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
    painter.drawImage(0, 0, destinationImage);
    painter.setCompositionMode(mode);
    painter.drawImage(0, 0, sourceImage);
    painter.setCompositionMode(QPainter::CompositionMode_DestinationOver);
    painter.fillRect(resultImage.rect(), Qt::white);
    painter.end();

    resultLabel->setPixmap(QPixmap::fromImage(resultImage));
}

To copy to clipboard, switch view to plain text mode

the above code is the part of the Image Composition Example

As per your program need you have to look at the Image Composition Example

**2lights** · 14th August 2013, 12:50

Getting there...

Remember, the image im loading is grayscale
Im converting it to Red/Green or Blue scale

I tried for testing purposes only,
I uploaded a color image...
the ConvertColor Function
instead of converting everyting to red(different shades of red), it made it black & white
but no "Index out of range error"

When I upload a grayscale image(program needs to do)
I get an Index out of range err in application output

Qt Code:

Switch view

QImage::setPixel: Index -16645630 out of range
QImage::setPixel: Index -16645630 out of range
QImage::setPixel: Index -16645630 out of range
QImage::setPixel: Index -16514044 out of range
QFSFileEngine::open: No file name specified

QImage::setPixel: Index -16645630 out of range
QImage::setPixel: Index -16645630 out of range
QImage::setPixel: Index -16645630 out of range
QImage::setPixel: Index -16514044 out of range
QFSFileEngine::open: No file name specified

To copy to clipboard, switch view to plain text mode

In the label the original image(grayscale image) is uploadded
no change in color

Qt Code:

Switch view

primaryImage.load(imageFileName1);
 
QRgb colour;
int newCol;
int width = primaryImage.width();
int height = primaryImage.height();
 
for(int i = 0; i < width; ++i)
{
for (int j = 0; j < height; ++j)
{
colour = primaryImage.pixel(i, j);
newCol = qRed(colour);
primaryImage.setPixel(i, j, qRgb(newCol, newCol, newCol));
}
}

primaryImage.load(imageFileName1);
 
QRgb colour;
int newCol;
int width = primaryImage.width();
int height = primaryImage.height();
 
for(int i = 0; i < width; ++i)
{
for (int j = 0; j < height; ++j)
{
colour = primaryImage.pixel(i, j);
newCol = qRed(colour);
primaryImage.setPixel(i, j, qRgb(newCol, newCol, newCol));
}
}

To copy to clipboard, switch view to plain text mode

Im not seeing the problem,

Solution?

Translation SOLVED.... Thanks

**karankumar1609** · 14th August 2013, 13:27

I tried for testing purposes only,
I uploaded a color image...
the ConvertColor Function
instead of converting everyting to red(different shades of red), it made it black & white
but no "Index out of range error"

Your grayscale image might be of different format.
Load it in QImage::Format_RGB32 and then use the same function. it will solve your index out of range problem.

try:

Qt Code:

Switch view

...
primaryImage.load(imageFileName1);
primaryImage = primaryImage.convertToFormat(QImage::Format_RGB32);
...

...
primaryImage.load(imageFileName1);
primaryImage = primaryImage.convertToFormat(QImage::Format_RGB32);
...

To copy to clipboard, switch view to plain text mode

**wysota** · 14th August 2013, 13:29

Originally Posted by 2lights

Remember, the image im loading is grayscale

If the image is originally grayscale then it is likely that it is indexed and if so, changing colours of the image can be simplified to modify just the color table.

E.g. to convert your image to shades of red, you'd do:

Qt Code:

Switch view

QImage img(...);
QVector<QRgb> colorTable = img.colorTable();
for(int i=0;i<colorTable.size();++i) {
  colorTable[i] = qRed(qGray(colorTable[i]));
}
img.setColorTable(colorTable);

QImage img(...);
QVector<QRgb> colorTable = img.colorTable();
for(int i=0;i<colorTable.size();++i) {
  colorTable[i] = qRed(qGray(colorTable[i]));
}
img.setColorTable(colorTable);

To copy to clipboard, switch view to plain text mode

Note -- the image has to be indexed and not true color!

**2lights** · 14th August 2013, 13:48

I created an if statement to check if grayscale.
image1.AllGray();

if(false)
@karankumar1609
That did solve the out of scope issue
though No Colour change on image

if(true){
@wysota
implemented wysota solution
Unfortunately, No Image is displayed at all

}

It seemed simple at first,
But now im just hitting barriers

Just to reiterate my problem
(Most of images are black and white and shades of gray)
and convert entire image to a shade of green, red or blue

Where am i going wrong?

**karankumar1609** · 14th August 2013, 13:56

well the above example should work for you.,
Please paste your code for more clarification on what exactly you are doing.

**wysota** · 14th August 2013, 13:56

Did you check if the image was indexed prior to implementing my solution?

**2lights** · 14th August 2013, 14:06

Not sure if im checking if image is indexed correctly
this is what i got: an if statement around your solution

Qt Code:

Switch view

if(image1.allGray()){ //if grayscale than it should be indexed... I think
    QVector<QRgb> colorTable = image1.colorTable();
    for(int i=0;i<colorTable.size();++i) {
    colorTable[i] = qRed(qGray(colorTable[i]));
    }

if(image1.allGray()){ //if grayscale than it should be indexed... I think
    QVector<QRgb> colorTable = image1.colorTable();
    for(int i=0;i<colorTable.size();++i) {
    colorTable[i] = qRed(qGray(colorTable[i]));
    }

To copy to clipboard, switch view to plain text mode

No image is shown

**karankumar1609** · 14th August 2013, 14:11

Implement this

Qt Code:

Switch view

...
...
image1.setColorTable(colorTable);

...
...
image1.setColorTable(colorTable);

To copy to clipboard, switch view to plain text mode

you just calculate the color table but u need to se the new color table to image1.

**2lights** · 14th August 2013, 14:20

I am setting the color table after the loop

This is my current function to load image

Qt Code:

Switch view

void Compare::getImageFileName1()
{
    fp1 = true;
    QFileDialog dialog(this, "Upload");
    dialog.setNameFilter(tr("Images (*.png *.xpm *.jpg *.bmp *.tif)"));
    dialog.setViewMode(QFileDialog::Detail);
 
    if(dialog.exec())
    {
        imageFileName1 = dialog.selectedFiles().first();
    }
 
    image1.load(imageFileName1);
    image1Width = image1.width();
    image1Height = image1.height();
 
    if(image1.allGray()){
    QVector<QRgb> colorTable = image1.colorTable();
    for(int i=0;i<colorTable.size();++i) {
    colorTable[i] = qRed(qGray(colorTable[i]));
    }
    image1.setColorTable(colorTable);
    }
    imageDrawFlag1 = true;
}

void Compare::getImageFileName1()
{
    fp1 = true;
    QFileDialog dialog(this, "Upload");
    dialog.setNameFilter(tr("Images (*.png *.xpm *.jpg *.bmp *.tif)"));
    dialog.setViewMode(QFileDialog::Detail);

    if(dialog.exec())
    {
        imageFileName1 = dialog.selectedFiles().first();
    }

    image1.load(imageFileName1);
    image1Width = image1.width();
    image1Height = image1.height();

    if(image1.allGray()){
    QVector<QRgb> colorTable = image1.colorTable();
    for(int i=0;i<colorTable.size();++i) {
    colorTable[i] = qRed(qGray(colorTable[i]));
    }
    image1.setColorTable(colorTable);
    }
    imageDrawFlag1 = true;
}

To copy to clipboard, switch view to plain text mode

In my paint function:

Qt Code:

Switch view

//Painting actual Image
if(imageDrawFlag1 == true){
painter.drawImage(QPoint(0, 0), image1);

//Painting actual Image
if(imageDrawFlag1 == true){
painter.drawImage(QPoint(0, 0), image1);

To copy to clipboard, switch view to plain text mode

Your time & help is much appreciated

**karankumar1609** · 14th August 2013, 14:30

code is correct, it exactly do what you write.
Well its my assumption you should call update(), may be your paint function not called after returning from the function.

Qt Code:

Switch view

void Compare::getImageFileName1()
    {
    fp1 = true;
    QFileDialog dialog(this, "Upload");
    dialog.setNameFilter(tr("Images (*.png *.xpm *.jpg *.bmp *.tif)"));
    dialog.setViewMode(QFileDialog::Detail);
 
    if(dialog.exec())
    {
    imageFileName1 = dialog.selectedFiles().first();
    }
 
    image1.load(imageFileName1);
    image1Width = image1.width();
    image1Height = image1.height();
 
    if(image1.allGray()){
    QVector<QRgb> colorTable = image1.colorTable();
    for(int i=0;i<colorTable.size();++i) {
    colorTable[i] = qRed(qGray(colorTable[i]));
    }
    image1.setColorTable(colorTable);
    }
    imageDrawFlag1 = true;
 
    update();
    }

void Compare::getImageFileName1()
    {
    fp1 = true;
    QFileDialog dialog(this, "Upload");
    dialog.setNameFilter(tr("Images (*.png *.xpm *.jpg *.bmp *.tif)"));
    dialog.setViewMode(QFileDialog::Detail);
     
    if(dialog.exec())
    {
    imageFileName1 = dialog.selectedFiles().first();
    }
     
    image1.load(imageFileName1);
    image1Width = image1.width();
    image1Height = image1.height();
     
    if(image1.allGray()){
    QVector<QRgb> colorTable = image1.colorTable();
    for(int i=0;i<colorTable.size();++i) {
    colorTable[i] = qRed(qGray(colorTable[i]));
    }
    image1.setColorTable(colorTable);
    }
    imageDrawFlag1 = true;

    update();
    }

To copy to clipboard, switch view to plain text mode

**wysota** · 14th August 2013, 15:16

Originally Posted by 2lights

Not sure if im checking if image is indexed correctly

Do you understand what an "indexed" image is? allGray() will not tell you if an image is indexed or not.

**2lights** · 14th August 2013, 15:48

Not sure what an indexed image is...
But the images that i will be loading will be grayscale images
& will have ext: .png *.xpm *.jpg *.bmp *.tif

I tried loading
Image is not uploaded

Maybe the image is being uploaded but the entire image is converted to the color gray!
hence it looks like no image is uploaded

I added

Qt Code:

Switch view

image1.convertToFormat(QImage::Format_Mono); // if not grayscale converting to grayscale

image1.convertToFormat(QImage::Format_Mono); // if not grayscale converting to grayscale

To copy to clipboard, switch view to plain text mode

Qt Code:

Switch view

QVector<QRgb> colorTable = image1.colorTable();
        for(int i=0;i<colorTable.size();++i)
        {
            colorTable[i] = qRed(qGray(colorTable[i]));
        }
        image1.setColorTable(colorTable);

QVector<QRgb> colorTable = image1.colorTable();
        for(int i=0;i<colorTable.size();++i)
        {
            colorTable[i] = qRed(qGray(colorTable[i]));
        }
        image1.setColorTable(colorTable);

To copy to clipboard, switch view to plain text mode

got rid of the iff statement

**wysota** · 14th August 2013, 18:52

Originally Posted by 2lights

Not sure what an indexed image is...

Go to QImage docs, press Ctrl+F or equivalent and type in "indexed".

Apart from that read this: http://en.wikipedia.org/wiki/Indexed_color

Thread: QImage Rotation and Translation & Invert Specific Colors

Thread Tools

Search Thread

Display

QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

The following user says thank you to karankumar1609 for this useful post:

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

The following user says thank you to wysota for this useful post:

Re: QImage Rotation and Translation & Invert Specific Colors

The following user says thank you to karankumar1609 for this useful post:

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

Re: QImage Rotation and Translation & Invert Specific Colors

Similar Threads

Background color substitution after applying rotation matrix on QImage.

Graph rotation

Ellipse and rotation

Rotation on Qframe

QImage (..) & QImage::save() always return NULL value - why?

Tags for this Thread

Bookmarks

Bookmarks

Posting Permissions