The Image widget

Author: Christian Mayer

Available since: 0.8.0 (2012)

Description

Adds an image to your visualization. Using the auto-refresh setting this widget can be used e.g. to show a camera picture.

Settings

For a general understanding of how the configuration files are structured and what elements and attributes are it is recommended to read this section first: Pages and structure of CometVisu.

The behaviour and appearance of the Image widget can be influenced by using certain attributes and elements. The following tables show the allowed attributes and elements and their possible values. The screenshots show, how both can be edited in the editor.

Attributes underlined by ….. are mandatory, all the others are optional and be omitted.

Allowed attributes in the Image-element

Element	Attribute
	Name	Content	Description
image	src	URI	Complete path (URI) to the picture
	width	dimension (number+unit)	Sets the width of the image. Format must be CSS (e.g. px, em, %).
	height	dimension (number+unit)	Sets the height of the image. Format must be CSS (e.g. px, em, %).
	widthfit	true or false
	crop-top	dimension (number+unit)	Sets the top crop of the image. Format must be absolute CSS (e.g. px, em).
	crop-bottom	dimension (number+unit)	Sets the bottom crop of the image. Format must be absolute CSS (e.g. px, em).
	refresh	decimal	Sets the update rate for the picture in seconds
	cachecontrol	full, force, weak or none	Set the cache control strategy for refresh.
	flavour	string	Selection of a display variant. See also Flavour.
	class	string	Add this value to the CSS class so that it can be formatted by a user provided style sheet.
	align	left, right or center
	placeholder	none, src, hide or exclude	Defined how to deal with the case when no image url is set

Valid values for cachecontrol are:

full Standard. By extending the URL with a timestamp a refresh is

ensured. Server support is required though.

force Using sophisticated methods an enforcement of the refresh is

attempted.

weak The URL will be extended by an anchor with timestamp. This will

work with most servers where full mode doesn’t work. But it requires the correct use of HTTP headers by the server as well as a correct reaction by the web browser.

none The URL will not be modified. A working refresh can be prevented

by caching.

Attributes in the editor (simple view) [1]

Allowed child-elements and their attributes

Element	Attribute
Structure	Name	Content	Description
image layout	colspan	decimal	Amount of columns this widget should be wide.
	colspan-m	decimal	Overrules the amount of columns on a medium screen.
	colspan-s	decimal	Overrules the amount of columns on a small screen.
	rowspan	decimal	Amount of rows this widget should be high.
	x	string	Horizontal position of the widget for 2D pages.
	x-s	string	Horizontal position of the widget for 2D pages on a small screen.
	x-m	string	Horizontal position of the widget for 2D pages on a medium screen.
	y	string	Vertical position of the widget for 2D pages.
	y-s	string	Vertical position of the widget for 2D pages on a small screen.
	y-m	string	Vertical position of the widget for 2D pages on a medium screen.
	z	string	Reserved for future use.
	width	string	Width for the widget for 2D pages.
	width-s	string	Width for the widget for 2D pages on a small screen.
	width-m	string	Width for the widget for 2D pages on a medium screen.
	scale	true or false	Enable/Disable scaling layout values relative to backdrop on 2d pages (default: true).
	scale-s	true or false	Enable/Disable scaling layout values relative to backdrop on 2d pages on a small screen (default: true).
	scale-m	true or false	Enable/Disable scaling layout values relative to backdrop on 2d pages on a medium screen (default: true).

Element	Attribute
Structure	Name	Content	Description
image label icon	name	string	Name of the icon registration.
	type	string
	flavour	string	Selection of a display variant. See also Flavour.
	color	string	Color of the icon in CSS notation (e.g. #1188FF).
	styling	string	Change the color of the displayed value depending on its value. See also Styling
	class	string	Add this value to the CSS class so that it can be formatted by a user provided style sheet.
image label #text		string	Text to display a label for the widget.

Element	Attribute
Structure	Name	Content	Description
image address	transform	string	Transformation of the bus system value to be shown.
	mode	disable, read, write or readwrite	“disable” deactivates the communication, “read” will only fetch data from the backend, “write” will only write to it and an address with “readwrite” will be both, read from and written to.
	variant	string
	format-pos	decimal	Position for format string when multiple addresses are used.
	selector	string	Only MQTT: JSON selector
	qos	decimal	Only MQTT: QoS
	retain	true or false	Only MQTT: retain flag
	ignore-error	true or false	Only MQTT: ignore decode errors.
image address #text		string	The GA (like: 12/0/7) for KNX-backends, the item name for openHAB-backend or the MQTT topic

Elements in the editor

Examples

It is possible to manually edit the visu_config.xml and add an entry for the Image widget.

Caution

Make sure that you only use UTF-8 encoded characters by settings the encoding in your XML-editor to UTF-8 mode!

<image src="resource/icons/CometVisu_orange.png" width="45px" height="32px">
  <layout colspan="2"/>
</image>

Footnotes

[1]

The simple view might not show everything. To see all elements/attributes use the expert view.