Scale Filter

The dependency of scaling and resolution is mostly misunderstood. You may use this filter to scale a document to a certain size.



Size or Factor
Chooses whether to use the given unit fields or the percent fields for scaling.

Width, Height
Selects the output size by unit.

%
Selects the output size by percent.

PopUp [cm, inch, points]
Determines the used units in the fields width and height.

Current, Button
Fetches the size from the current active document.

keep ratio
Checked it will automatically set the corresponding field of width or height. To check it you need an active document.

retain resolution
If this button is checked, the scaled image will have the same resolution (dpi) as the original image. That means, an image originally scanned with 100 dpi, scaled by 50% will again have 100 dpi but only half of the width and height. Corresponding the real data size is reduced to a quarter of the original image. Of course you loose quality when printing or in further image operations.
If the button stays unchecked, the real data size won't be changed. All we do is to scale some of the image information data, which contains the geometric size information. An image scanned with 100 dpi and scaled by 50% will then have half of the width and height, but the double resolution (here 200 dpi). Of course the real data size won't change and the quality when printing will be the same (or better).

High quality
Uses a time intensive scaling algorithm, which interpolates the image data.
 
Note: The units as displayed on screen or used in the datafields may not reflect the reality, but are calculated out of the relation of scanned resolution and size.
E.g. If you want to have an image where the real contained data is equal to the given unit pixel you would have to scan it with 72 dpi.

See also