I am pushing QImage into doing something it was probably not designed for...  namely, printing very accurate drawings for graphics arts purposes.  The print has to be pixel perfect (i.e., one inch in the image has to equal exactly one inch on paper when it is printed).

So I save a monochrome bitmap (BMP) image with 1200 dpi resolution, which I then place on a QImage page, as you would with any other image.

This brings me to the question:

When "Auto Crop" is turned on, the image is resized to fit whatever size I have chosen on the "Prints" tab - which is as I would expect.

However...  when I turn off Auto Crop by clicking the scissors with the image selected on the page, it is resized to something much bigger than it actually should be, at 300dpi...  it becomes 4x too large.

What I was hoping for was that the original resolution / size of the image would "survive" into the print on the QImage page, like a normal image does.

Is this some kind of issue with using monochrome bitmaps?  (It works perfectly in every other respect and prints beautifully when Auto Crop is on, but it is a pain to resize the Print every time).

Try this:
Open the print size box and select CUSTOM.
Then look at the upper right corner (Override BOX) Type in 1200 and put a check in Over ride. Screen snaps 002 and 003
Then OK. Back to the main screen, add your image, it will be 1200 ppi.
Terry called me to help. He is visiting and only has his smart phone. No screen snapper.
Fred

Apologies for being so SLOOOW to respond to this!

Terry-M's trick of using "Original Size" on the print size is what was needed.

I'm printing on 24" roll paper.  The largest image I've printed with QImage is 24" by 96".  Awesome!