hi,
let say you would like to fill an ellipse with a color. the color should be related to the x position of the mouse.
like if x is 0 the color should be black...
but what would happen if your canvas size is bigger then 255 ?? you will probably get an error.
so what you need to do is get a number with the same ratio as the coordinate u want to use but that will fit your needs.
EXAMPLE:
Canvas = 0 to 640 (width/x axis)
Color = 0 to 255
now according to my x position in that canvas i would like to get a number between 0 and 255
so we could use this function:
we put the X position and the space from minimum to maximum of that x position (= canvas size) and the limits from the new minimum and maximum range we would like to get.
like:
what we do here is we draw an ellipse that's size is between 50 and 100 and fill it with a color between 0 and 255. even if we use our x coordinate we can still get the number we need with the same ratio.
this is very useful if you need to get a number in a specific range but would like to use a bigger range as the reference (like mouse coordinates, slider (0-100), progressbar (0-100),...)
i dont know if such function already exists in b4x, i just saw it in another coding language and came with that function in b4j.
regards, ilan
let say you would like to fill an ellipse with a color. the color should be related to the x position of the mouse.
like if x is 0 the color should be black...
but what would happen if your canvas size is bigger then 255 ?? you will probably get an error.
so what you need to do is get a number with the same ratio as the coordinate u want to use but that will fit your needs.
EXAMPLE:
Canvas = 0 to 640 (width/x axis)
Color = 0 to 255
now according to my x position in that canvas i would like to get a number between 0 and 255
so we could use this function:
B4X:
Sub mapping(var As Float, min_real As Float, max_real As Float, min_scaled As Float, max_scaled As Float) As Float
Return (var * ((max_scaled-min_scaled) / (max_real-min_real))) + min_scaled
End Subwe put the X position and the space from minimum to maximum of that x position (= canvas size) and the limits from the new minimum and maximum range we would like to get.
like:
B4X:
#Region Project Attributes
#MainFormWidth: 600
#MainFormHeight: 400
#End Region
Sub Process_Globals
Private fx As JFX
Private MainForm As Form
Dim c As Canvas
End Sub
Sub AppStart (Form1 As Form, Args() As String)
MainForm = Form1
MainForm.SetFormStyle("UNIFIED")
MainForm.Show
c.Initialize("c")
MainForm.RootPane.AddNode(c,0,0,MainForm.RootPane.Width,MainForm.RootPane.Height)
End Sub
Sub mapping(var As Float, min_real As Float, max_real As Float, min_scaled As Float, max_scaled As Float) As Float
Return (var * ((max_scaled-min_scaled) / (max_real-min_real))) + min_scaled
End Sub
Sub MainForm_MouseMoved (EventData As MouseEvent)
c.ClearRect(0,0,c.Width,c.Height)
c.DrawCircle(c.Width/2,c.Height/2,mapping(EventData.X,0,c.Width,50,100),fx.Colors.RGB(255,mapping(EventData.X,0,c.Width,0,255),0),True,1)
End Subwhat we do here is we draw an ellipse that's size is between 50 and 100 and fill it with a color between 0 and 255. even if we use our x coordinate we can still get the number we need with the same ratio.
this is very useful if you need to get a number in a specific range but would like to use a bigger range as the reference (like mouse coordinates, slider (0-100), progressbar (0-100),...)
i dont know if such function already exists in b4x, i just saw it in another coding language and came with that function in b4j.
regards, ilan