I copy and paste an image from one file and into another and a message asks if I want to resample the pasted image. I tried it both ways, the first time I did not resample the image and it appears much smaller than the image it is being pasted into. The second time I resampled the image and it displays larger, though it does not seem pixelated.
1. By resampling, is this stretching the image?
2. If so, how does it decide how much larger to make the image?
It is trying to match the resolution (pixels per inch) of the pasted image to the one already on the canvas.
Here's a quick way to see clearly what's happening;
a. Create a new document 100 x 100 px with a resolution of 100 pixels per inch
b. Create another new document 100 x 100 px with a resolution of 200 pixels per inch
c. In the second document draw out a vector rectangle 100 x 100 pixels
d. Cut the rectangle and paste it into the first document
At this point you get the dialog box that tells you the pasted image has a different resolution and asks if you want to resample or not.
e. Select "Don't Resample"
The pasted rectangle is now the same size as the document it's pasted into and hasn't been resized at all, therefore no resampling and no image degradation for bitmapped images.
f. delete the pasted rectangle and paste again this time using "Resample"
The pasted rectangle is now exactly half the size, 50 x 50 px, of the document it's pasted into. That's because the pasted object, that was originally 100 x 100 px at 200 pixels per inch, has now been resampled in size, to match the resolution of the document, 100 pixels per inch, it's been pasted into.
If the pasted object was originally 100 x 100 px at 400 pixels per inch the final resampled size would have been 25 x 25 px.
Hope this helps.