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app[screen] RPi screen capture

Screen capture utility

Implements the screen capture tool to return screenshot of display to remote U8 systems.
To install the app, evaluate in a connected workspace:
SwikiCodeRobot @> #(app screen)
After installation, you can connect a remote S8 system to browse the running system and captures creen are served as images.

Prerequisites

"Ensure required libraries are loaded"
self require: #FFIDynamicLibrary in: #(
	'build/node/library/node-ffi/node-ffi.st.js'
	'u8:aleReimondo/node-ffi/node-ffi.st.js'
); require: #X11 in: #(
	'build/node/library/RaspberryPi/X11.st.js'
	'u8:aleReimondo/RaspberryPi/X11.st.js'
); require: #Imlib2 in: #(
	'build/node/library/RaspberryPi/Imlib2.st.js'
	'u8:aleReimondo/RaspberryPi/Imlib2.st.js'
).!
X11 current isNil ifTrue: [
	self print: '// Missing X11 library'.
	^self abort
].
Imlib2 current isNil ifTrue: [
	self print: '// Missing Imlib2 library'.
	^self abort
].
(Imlib2 class >> #captureUrl) notNil ifTrue: [
	self print: '// The screen capture application is already installed. Browse references to #captureUrl'.
	^self abort
].




! Imlib2 class methodsFor: #snapshot !
snapshot
	" Returns an image captured from Display. "

	| x11 display screen number visual depth colormap width height root |
	x11	:= X11 current.
	display	:= x11 XOpenDisplay: nil json.
	screen	:= x11 XDefaultScreenOfDisplay: display.
	number	:= x11 XScreenNumberOfScreen: screen.
	visual	:= x11 XDefaultVisual: display screenNumber: number.
	depth	:= x11 XDefaultDepth: display screenNumber: number.
	colormap:= x11 XDefaultColormap: display screenNumber: number.
	root	:= x11 XRootWindow: display screenNumber: number.
	width	:= x11 XDisplayWidth: display screenNumber: number.
	height	:= x11 XDisplayHeight: display screenNumber: number.

	Imlib2 current
		imlib_context_set_display: display;
		imlib_context_set_visual: visual;
		imlib_context_set_colormap: colormap;
		imlib_context_set_color_modifier: nil json;
		imlib_context_set_operation: 0"IMLIB_OP_COPY";
		yourself.

	^self current
		imlib_context_set_drawable: root;
		imlib_create_image_from_drawable: 0 x: 0 y: 0
		width: width height: height needToGrabX: 1! !

! Imlib2 class methodsFor: #snapshot !
saveSnapshot: pathName
	" Capture image from Display and save it in snapshot file at pathName. "

	self current
		imlib_context_set_image: self snapshot;
		imlib_save_image: pathName;
		yourself.! !

! Imlib2 class methodsFor: #platform-tools !
captureUrl
	" Returns the URL of an image captured from Display. "

	| fileName base64 |
	fileName := 'Snapshot.png'.
	self saveSnapshot: fileName.
	base64 := (NodeJS fs readFileSync: fileName) toString: #base64.
	^'data:image/png;base64,' ,base64! !



"Install screen capture tool"
! Smalltalk methodsFor: #platform-tools !
screen: aBlock
	" Evaluate aBlock with the (captured) screen of the receiver. "

	^Imlib2 captureUrl! !



"Screen capture tool installed"
self print: 'Now you can open/refresh the screen of connected system to get the image of Display.'