Display images (native)

Owned by Andy Erd
Mar 31, 2022
2 min read

Black and white devices

The library provides a function SetSignBackground
which you may use to show a background on the display while signing.
It is recommended to pass black and white images
since this is what the black and white devices can render.
If color images are passed, the library converts them to 1 bpp-Bitmaps.

Color pads

The color pads can show images in different ways different modes of operations.
  1. The Customer logo mode can shows a sequence of images.
  2. The document viewing mode shows an image that is part of a document.
  3. The document signing mode. Like document viewing mode. Can capture a signature.
  4. The continuous scroll shows an image which is part of a document.
    Enables scrolling continuously through the document.
  5. Simple dialog mode allows to draw text and to display images
    at arbitrary positions on the device display.
Not all color models support all the listed modes.

Customer logo mode

The images shown in he customer logo mode need to be uploaded to the device.
After the images have been uploaded, switch to customer logo mode
Then, the uploaded images are shown sequentially.
For removing uploaded screens, the library provides the function RemovePromoscreen.
 
If the signature device supports portrait orientation,
there are two sequences of images for the customer logo mode;
one for landscape orientation and another for portrait orientation.

The Document viewing mode

allows for display of paginated documents.
To that end, the document has to split into a number of images (pages).
Then, the first page to be displayed needs to be transferred to the device
together with its page number and the total number of pages.
The document viewing mode has buttons
two of which lend itself for document navigation,
  • the next button and
  • the previous button.
This purpose can be achieved by using a button callback
and transfer the next/previous page if the next/previous button has been clicked.
 

The Document signing mode

The document signing mode can capture signatures while displaying a background image.
This background image as well as the signature rectangle need to be set

Scrolling the signature rectangle

Here, the signature rectangle is the rectangular region
atop the displayed image where the device captures the drawing.
Some devices can scroll the signature rectangle across the display together with the background image.
 

The continuous scroll mode

shows a document through which the user can scroll with the pen.

To that end the document has to be split into a sequence of tiles.
 
When the device has been set to continuous scroll mode
individual tiles will be requested through a callback.
The requested tiles have to be uploaded.
 
For example, if the device is displaying tile 7 and the user scrolls down,
the tiles 8, 9, (and so on) will be requested next.
An exception to this rule is when the user scrolls sufficiently fast.
Then the device may skip some tiles until scrolling becomes slow.