QImage Rotation and Translation & Invert Specific Colors

[karankumar1609]

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

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));
}

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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]

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

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

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

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));
}
}

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Im not seeing the problem,
Solution?

Translation SOLVED.... Thanks

[karankumar1609]

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:

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

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

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[wysota]

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:

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);

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

[2lights]

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]

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

[wysota]

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

[2lights]

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

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]));
    }

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No image is shown

[karankumar1609]

Implement this

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

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

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

[2lights]

I am setting the color table after the loop

This is my current function to load image

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;
}

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In my paint function:

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

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

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Your time & help is much appreciated

[karankumar1609]

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.

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();
    }

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[wysota]

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]

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

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

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

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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);

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got rid of the iff statement

[wysota]

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

[2lights]

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