Change the Size of a Raster From a Grip Point
You can change the size of a raster from a grip point either by stretching freely or in such a way that the aspect ratio is kept.
Keep the Aspect Ratio

- Select the raster.
 - Click a corner grip point.
 - Click the new location.
 
Stretch Freely

- Select the raster.
 - Move the cursor near a corner grip point, open the context-sensitive menu by right-clicking, and select Stretch.
 - Click the new location.
 
Note: 
  - If you want to change the scale of a raster by using a scale factor or a reference dimension, move the raster either from the grip point or by using the 
 Move Raster Image function. 
