The Choices window
The choices dialogue box can be accessed either
by clicking on the icon bar icon with Adjust, or by selecting
'Choices' from the icon bar icon menu. Either approach will open a
window. Across the top is a strip of file type icons. Clicking on
these icons, will open a sub configuration window for the file
type.
The options provided for the file types are discussed below. The arrows at either end of the strip allow the available file types to be scrolled through.
Across the bottom of the configuration window is another row of icons. These allow various aspects of the program to be controlled. Each icon represents a group of related parameters. Again configuration windows can be opened by clicking on the icons.
Finally there is a 'Save' button. Clicking on this will save the configuration of the program so that it is the same when the program is next used.
Memory

This controls the programs use of memory. The top slider lets you set the maximum amount of RAM that it will use. The next two bars cannot be adjusted, they show the amount of RAM in use, and the amount of disc space being used as virtual memory.
Note that these bars can be confusing. The RAM bars show the proportion of the total RAM in the computer. The disc bar shows the proportion of free disc space in use. The free space on the disc may be much larger or possibly smaller than RAM. You should not make relative comparisons of the RAM and Disc bars.
The writable icon 'Temporary file' allows the directory where the temporary file holding image data which will not fit in RAM is held. Clicking on the right pointing arrow to the side of this, will pop up a standard save box. The icon may be dragged to where you want the temporary file to be held. Note that if a temporary file already exists, you cannot change the location immediately this way.
It may be useful to leave the memory box open to give you some idea as to how much memory you are using. The RAM and Disc bars will be continuously updated.
The temporary file should be kept on a large area of fast writable disc. By default it is created inside the directory !Scrap. It is not a good idea to put the temporary file on a RAM disc. Doing so defeats the object, and the program can make use of any spare RAM more efficiently itself, rather than via a RAM disc.
Usually the temporary file will only become active when large images are being handled, in such cases you must have plenty of free space on the disc. At any rate using virtual memory requires large areas of empty disc space. When virtual memory is in use, the general operation of DPlngScan will become much slower, since in general reads and writes to RAM will be much faster than to disc. Thus it is sensible to keep the max RAM as high as is practical.
Windows
The five buttons on this window control the default appearance of
each new window. Whether the window will have rulers, a toolbox, an
info palette, if dithering will be enabled for it, and whether printer
margins will be shown.
Page
This allows the default page size, units and X and Y resolutions to
be chosen, by clicking on the appropriate menu button to the right, and
making a selection from the resulting menu.
General
Alias filter type
This allows the Aliasing filter used for the operations on the Edit menu to be set.
Colour weights
Three writable icons which set the weights used when greyscaling images.
Long process
This allows you to specify what will happen whilst the program is busy working on a long process. The alternatives are to display the hourglass with a % sign, to multitask (which means you can carry on doing other things) or finally to blank the screen. Blanking the screen is useful because in screen modes with lots of colours and pixels the older Acorn computers run much more slowly. Multitasking will be the slowest option, and it is not always possible to multitask for example when transferring files to other applications. It is possible to arrange for an audible 'beep' to be made at the start and end of each multi tasking process to give some sort of feedback.
Which of these options you choose will depend on how you work. For slow machines the multi tasking option may be useful. For large screen modes blanking will be most suitable. For a fast machine the hourglass is probably best.
Undo steps
This allows the number of undo steps to be set. Increasing the number will use more RAM/disc space. On modern hardware, with 2GB RAM usable by RISC OS, several undo steps can be stored in memory for quite large images. More undo steps allows more flexibility when experimenting with editing images - if you do not like the result of one or more operations, the use of the Undo button allows the action to be reversed. The undo image data will be stored on disc if there is insufficient RAM available.
Histogram levels
This sets the default number of histogram levels used in the Histogram dialogue (from the main menu Filter-Histogram).
Auto-add file extension
If this is ticked, then when the image format is changed in the Save as dialogue, the file extension will be automatically added to the file name. If you wish to automatically add file extensions for sprite or draw files, then you need to also tick the option in the Sprite or Draw file dialogues. See the next section below. Some applications on foreign OS recognise these extension, e.g. Ovation Pro for Windows.
Auto scaling on load
This section determines how DPScan displays images on first load. The previous behaviour (versions up to 1.30) simply displayed the image at 100% scale in a relatively small window. Larger images showed only a small part of the image, thus requiring adjustment of e.g. zoom ratio to show the whole image on-screen. If nothing in this section is ticked, the behaviour continues to be the same as previously.
When Auto scale image on load is ticked, then when an image is dragged to the iconbar icon, or is double clicked in a filer window, and it is too large to show the whole image on screen at 100% zoom, the image will be zoomed to a smaller scale so it just fills the screen. If an image is dragged in to an already open window, then it is zoomed down to fit the existing window if necessary. The additional option Do not cover iconbar sets whether the whole screen is used, or whether the iconbar is left uncovered, when opening new windows.
If the option Autoset page size on load is ticked, then the image size will be compared with the default page size, and if the image is larger than this page size, the page size will be increased (for this document only) to include the whole image.
There is an additional option Allow custom page sizes. If this is not ticked, then the configured page sizes (as in the main menu file-page size) will be used. If ticked, then DPScan will calculate a page size sufficient to include the whole image, but not necessarily as large as the next higher metric A size. For very large images that are bigger than the 4A0 page size, a custom size will always be used.