Size photo so it will consistently print at a specific size
Whenever I know I want to print a photo at a certain size, Ibring it into GIMP, and re-export it immediately, changing thename to photoXXX_8x10.jpeg. (So as not to accidentally killthe original file)I then do a rectangle select, and in the Tool Options section, click on Fixed -- Aspect Ratio, and enter 8:10 (for example) inthe box below. I then click 'n' drag in the image. The boxI make will be the right shape for the print (or I then go back andmake it 10x8, 'cause I got it in the wrong order...!).I release the left mouse button, and then use the side and
corner buttons to enlarge the box, and click 'n' drag in the centerto drag the box around. Once the box contains all that I want toinclude in the photo, I press Enter to 'finalize' the selection (clickinside the selection to get the 'handles' back to further modify thesize/position).Once you have a finalized selection, the menu option Image->FitCanvas To Selection modifies the image dimensions to match the newsize/shape of the image. Export this, and you have something thatwill exactly match the shape of the paper on which you want to print.
(Sometimes I don't want to crop ANY of the image, and then I just makeone of the dimensions LARGER than in the old image size, and just live with the fact that there will be white borders on two sides of the image.You may need to enlarge the canvas, and make a layer underneath your image, filled with white, to do this. You MIGHT choose,if your image is bordered with black, to fill this layer with black instead.)