Image Based Text Recognition
2. Character Image Collections
3. Character Capture Wizard
Image Based Text Recognition (IBTR) is
T-Plan Robot Enterprise 3.0 allowing to recognize
text and its coordinates on the
screen based on a collection of presaved characters.
The IBTR functionality consists of three components:
This feature is not parameter compatible with the Image Based Text Recognition plugin provided as an add-on for the
2.x releases. To convert the plugin based script code replace the tolerance
parameter with the passrate one where
- The "text" comparison method which is described in the Scripting Language
- Character image collections,
- Character Capture wizard.
passrate = 100 * (1 -
An approximate table of the sample tolerance values converted to pass
2. Character Image Collections
A Character Image Collection
is a directory with character images which meets these conventions:
An example of a character collection containing two variants of the 'a'
character and one 'o' character may look like:
- The collection directory contains just
folders named 'uNNNN' (a "character
folder") where 'NNNN' is the four digit upper case hexadecimal
UTF-8 character code. For example, the 'M' character must be
represented by a folder called 'u004D' because its UTF-8 code is
- Each character folder contains one or
more character images in a Java supported lossless format (PNG is
preferred, BMP is also supported but tends to be large). The image file
names are not relevant but the file extensions must be correct with
regard to the image format. For example, a PNG image must be stored in
a file with the ".png" extension.
Though Robot supports creation and maintenance of character image
collections through the Character Capture Wizard,
be created and edited by hand or in third
party image editors provided that the conventions are met. This
may be useful to exploit some features of the image
algorithm used internally by the IBTR. For example, to
create a character collection which would work on any background one
may edit the character images in an image editor and make the
background transparent or translucent.
- As the internal algorithm derives the
height of the text line and the space size from the collection images,
do not mix images of characters of different
size into a single collection. Mixing of
character images of different font and background colors is OK as
long as the characters are of the same font type and size.
3.2 Character Capture Wizard
The Character Capture Wizard
is the front end GUI window allowing to create, view and maintain
character image collections. The wizard can be started through the Tools->Character
Capture menu item.
The very first wizard screen titled Select Image Collection
deals with selection ot the character image directory to work with:
Collection button is enabled only if the Collection field
contains an existing directory. It opens a new window with the
collection details consisting of a tree of character images and a UTF-8
char set table showing which characters are covered by the collection.
The viewer also allows basic maintenance tasks such as editing or
deletion of the character images.
To add new character images to the selected collection click Next to proceed
to the Select Text
screen. Note that this button is enabled only when Robot is connected
to a desktop. If you need to extract characters from a static image
stored to a file, use the Login
Window to load the image though the Static Image Client.
To extract new characters from the screen perform the following steps:
Once you have selected the image and provided the text hit Next to proceed
to the last screen called Confirm Character Images:
- Click the Select Text Area
button. It will open a new window with a copy of the remote desktop.
Then drag your mouse in the image to mark the area containing text. See
the recommendations chapter below for
text selection tips. Once you are satisfied click either the green tick
button next to the selection or the Save & Close button on
the tool bar.
- Type the text the image contains into
the editor situated above the button. Make sure to provide it exactly
as it is displayed with all spaces and lines.
This screen shows the list of characters contained in the provided
text. If Robot recognizes the individual characters on the pixel level
in the image the list gets populated with the suggested character
images. Characters may be removed or modified the the Delete and Edit buttons. Be
aware that you don't have to deal with duplicate images. If a character
image already exists and it is the same as the newly extracted one, it
will be skipped automatically.
In some scenarios Robot may fail to parse the text area image for
individual characters. This may happen for example when the selected
text area does not meet the recommendations
criteria. Unrecognized characters then appear in the list with the
red N/A icon
This behavior does not mean that the character can not be searched
using the character collections. It merely indicates that the wizard
was not able to suggest the character image. To fix this simply select
the character in the list, click Edit and define
the its image in the text area manually.
These tips suggest how to select the text area on the screen in order
to minimize the number of unrecognized characters (N/A) which
have to be fixed manually:
- The very first pixel of the selected
area (the top left corner) must be of the background color.
- The area should contain text of a single
font type, size and color displayed on a solid color background such as
for example a block of black text on a white background. If the text
does not meet these requirements process it in smaller parts which meet
this criteria (by words and/or lines).
- The area should contain one continuous
block of text displayed on a single graphical component, such as a text
message, a button label, a menu item etc.. Do not select for example an
area which contains two or more buttons because their texts may be
aligned differently along the horizontal axis.
- As Robot separates the characters by
looking for a space of background color between them, fonts where
characters overlap along the vertical or horizontal axis fail to parse
and must be extracted manually. If such a character image contains
parts of another character, these must be removed in a third party
image editor such as Gimp and the affected must be made transparent to
make the character search algorithm skip them.