Why does GIMP resize my image?

[clarkleach]

Why, when I drop an image into GIMP, does it instantly get resized?  I know I'm probably doing something wrong.
I have an image that I want to rotate -45° and save without any further modification.
I want every pixel just as when it was loaded, just rotated.

[rich2005]

Well Gimp does not do anything of its own accord.

Quote:Why, when I drop an image into GIMP, does it instantly get resized?

More info required but as a first guess, are you using 'real world' units (inches / millimetres) and dropping an image into another image.

Gimp works in pixels and drop one image into another image, the pixel size does not change but if the image resolutions pixels-per-inch ppi differ then the ppi of the dropped in image now matches the base image. You can check the ppi from Image -> Print Size

Quote:I have an image that I want to rotate -45° and save without any further modification.
I want every pixel just as when it was loaded, just rotated.

As a single image example, Image -> Transform -> Arbitrary Rotation (say -45⁰) does just that. Why does the image size increase. The image is measured in pixels Width and Height, a rectangle and those are what were the diagonals. Makes a larger size canvas but your image in the canvas is still the same although rotated.

This a little animation 40 seconds https://i.imgur.com/MG6C3gZ.mp4 I put the print size into the title bar, keep an eye on it.
shows
Dropping a 72 ppi image into a 300 ppi image. It is the same if you open as layers.
Rotating an image and the increase in canvas size.
Dropping that into the 300 ppi canvas as another example.

Not the question you want answered, give a few more details and a screenshot.