qt - While rotation of Images, Size of image decreases -

hello all, trying rotate images in qt. while rotating again , again, size of image decreases. how can stop size decrement ? please me out. using code.

void mywidget::rotatelabel() {     qpixmap pixmap(*my_label->pixmap());     qmatrix rm;     rm.rotate(90);     pixmap = pixmap.transformed(rm);     my_label->setpixmap(pixmap); } 

in qt files qpixmap::transformed, states: -

the transformation transform internally adjusted compensate unwanted translation; i.e. pixmap produced smallest pixmap contains transformed points of original pixmap. use truematrix() function retrieve actual matrix used transforming pixmap.

i assume width , height of image not equal. therefore, you've observed, each rotation reduce size, ensure full image maintained.

change original image have equal width , height adding border, or scale image before or after rotation, image quality suffer.

alternatively, if you're rotating 90 degrees, rotate images in external art program, load 4 images , set 1 want, rather rotating them via qt.

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in response comments of having varying rotations, need ensure have source image never rotated, each iteration, create image source image need prevent both reduction in image size , image quality.

in pseudo code this: -

image srcimage(":/myimage");  void mywidget::rotatelabel() {     image img(srcimage);     img.rotate(rotation);     label->setpixmap(img); }