Cut an image using .tif file

[marpet]

The dimension is probably different because the second one is reprojected.
If once explained the change of geometry here:

S3-OLCI Subset Issues

Hi, I understand your confusion but I think I can explain. The round you observe is not really a rounding. The pixel closest to the entered location is looked up and set as pixel-location on the other tab. The the geo-location of this pixel is updated in the “Geo Coordinates” tab. Regarding the cut at the edges. If you have a look at the 4 corners of you subset you should still see the values you have entered. At least roughly. If you have a look the blue top left geometry and the yellow bo…

The color changes because the colours depend on the value range. You can specify specific upper and lower limits in the colour manipulation. (Why image colour changed after coregistraion? - #11 by ABraun)
For RGB images it is explained in the FAQ.