B4J Code Snippet Cool zooming effect

moster67

Expert
Licensed User
Found some code ages ago when I was looking into how to zoom images.

It uses a javafx.geometry.Rectangle2D object as a ViewPort and a method of the ImageView which sets the ViewPort (called setViewport). I haven't seen this available in B4J so I adapted the code to work with B4J.

This zooming effect can probably be made in other ways by just using native B4J skipping calling not exposed objects/methods with JavaObject.
I am also sure the code can be optimized so please be my guest to do so if you wish...

test.gif


The code:

B4X:
#Region Project Attributes
    #MainFormWidth: 650
    #MainFormHeight: 246
#End Region

Sub Process_Globals
    Private fx As JFX
    Private MainForm As Form
    Dim vpWidth As Double = 100
    Dim vpHeight As Double = 70
    Private Root1 As AnchorPane
    Private scaledImage As Pane
    Dim img As ImageView
    Dim scale As Double = 3
End Sub

Sub AppStart (Form1 As Form, Args() As String)
    MainForm = Form1
    'MainForm.RootPane.LoadLayout("Layout1") 'Load the layout file.
    Load
    MainForm.Show
 
End Sub

Sub Load
    img.Initialize("")
    img.SetImage(fx.LoadImage(File.DirAssets,"b4x.png"))
    '//setCache to impove performance
    Dim joImg As JavaObject = img
    joImg.RunMethod("setCache",Array(True))
 
    Dim image_background As ImageView
    image_background.Initialize("")
    image_background.SetImage(fx.LoadImage(File.DirAssets,"b4x.png"))
    '//setCache to impove performance
    Dim joImgBG As JavaObject = image_background
    joImgBG.RunMethod("setCache",Array(True))
 
    Root1.Initialize("")
    '//displays the scaled image
    scaledImage.Initialize("scaledImage")
 
    '//an image part specified by coordinates ,width and height
    Dim viewPort As JavaObject
    viewPort.InitializeNewInstance("javafx.geometry.Rectangle2D",Array(0.0,0.0,vpWidth,vpHeight))
    joImg.RunMethod("setViewport",Array(viewPort))
 
    '//add the scaled image to imageScale pane
    scaledImage.AddNode(joImg,0,0,-1,-1)
 
    Root1.AddNode(joImgBG,0,0,-1,-1)
    Root1.AddNode(scaledImage,0,0,-1,-1)
    MainForm.RootPane.AddNode(Root1,0,0,-1,-1)
 
End Sub

Sub scaledImage_MouseDragged (EventData As MouseEvent)
 
    Dim joScaledImg As JavaObject = scaledImage
    Dim joED As JavaObject = EventData
    Dim SceneX As Double = joED.RunMethod("getSceneX",Null)
    Dim SceneY As Double = joED.RunMethod("getSceneY",Null)
    joScaledImg.RunMethod("setLayoutX",Array(SceneX - (vpWidth/2))) 'center the mouse
    joScaledImg.RunMethod("setLayoutY",Array(SceneY - (vpHeight/2))) 'center the mouse
    Dim viewPort As JavaObject
    viewPort.InitializeNewInstance("javafx.geometry.Rectangle2D",Array(SceneX-(vpWidth/2), SceneY-(vpHeight/2), vpWidth, vpHeight))
    Dim joImg As JavaObject = img
    joImg.RunMethod("setViewport",Array(viewPort))
    joImg.RunMethod("setScaleX",Array(scale))
    joImg.RunMethod("setScaleY",Array(scale))
    joImg.RunMethod("setCache",Array(True))
    joImg.RunMethod("setPreserveRatio",Array(True))
 
End Sub

Sub scaledImage_MouseReleased (EventData As MouseEvent)
    Load
End Sub

'Return true to allow the default exceptions handler to handle the uncaught exception.
Sub Application_Error (Error As Exception, StackTrace As String) As Boolean
    Return True
End Sub
If you want to change the zoom level, just play around with the Scale variable.

Ps: sample project attached as well

Enjoy.
 

Attachments

Last edited:
Top