DrawPicture with Transfer Modes

General
1

Using only the “plain vanilla” methods of Xojo, is it possible to DrawPicture on a picture, using transfer modes, like Multiply, Screen, Overlay, etc?

2

Haven’t tried yet, but if the image is not too big (no more than 2048x2048, let’s say), using the RGBSurface property could be fast enough?

3

fast means 60 FPS? or seconds?

4

Well, I don’t need it for animation but if the calculation between two 2048x2046 RBGsurfaces could be performed in under a 1/10 of a second, I guess it would be enough.

5

i remember its slow (at least from debug mode) but you can test yourself.
i used this to remove a green background from a photo.

Public Function Alpha(red as Integer, green as Integer, blue as Integer) As Integer
  'Color Difference Key
  
  Return green-Max(red,blue)
  
End Function


Public Function RemoveGreen(picIn As Picture) As Picture

  Var picOut As New Picture(picIn.Width,picIn.Height)
  picOut.Graphics.DrawPicture(picIn,0,0)
  
  Var surf As RGBSurface = picOut.RGBSurface
  
  Var c As Color
  For x As Integer = 0 To picIn.Width-1
    For y As Integer = 0 To picIn.Height-1
      c = surf.Pixel(x,y)
      
      If Alpha(c.Red,c.Green,c.Blue) > 30  Then 
        surf.Pixel(x,y) = Color.Clear
      Else
        'surf.Pixel(x,y) = c
      End If
    Next
  Next
  
  Return picOut
  
End Function
6

Thank you so much.
I will give it a try.
Anyway, when compiled and with Agressive optimization, it should be faster, right?

1 Like
7

yes compiled is much faster than run from debug mode.
if you have benefit from optimization you will see.

8

Hello
i have some quick image warping routines
less than 1 second
an approach only with Drawpicture instead of RGBsurface

I also tried the new graphics functions
the new graphics functions are very difficult
with the drawing
I prefer my old pixmapshape elements
which I manage in an array

https://www.dropbox.com/s/l23qnivpwxv9y8o/drawpicture-Examble-fast.xojo_binary_project?dl=1

9

It is not possible.
As a test, I performed a Multiply transfer operation between 8 layers of 1024x800 pixels.
It took around 5 seconds.
Not fast enough :pensive:

10

you can only try to optimize it by static variables, var definition at top of the method, less methods calls, Pragma Directives.
but it will still use a single cpu core.
plan b would be a external command line tool for this task in c++ or using mbs plugins.

11

If you inline your calculations, you can save some time there.

12

How is that?!? :thinking:

13

Reducing the calls to functions, reduces the overheads involved in calling functions. You can also do this along the hue channel color.hue using a distance calculation to determine how far away from green it is.

14

Thank you. I will try that.
Also…
What is faster?
A Select Case, or IF statements, including a Continue to advance to the next iteration?

15

This is my code:

Var x,y,l As Integer
Var cor1,cor2 As Color
var r1,g1,b1,r2,g2,b2 As Double
Var final As New Picture(1024,800,32)

for y = 0 to 799
  for x = 0 to 1023
    cor1 = layer(layer1).RGBSurface.Pixel(x,y)
    for l = layer1+1 to layer2
      
      cor2 = layer(l).RGBSurface.Pixel(x,y)
      
      Select Case mode
      Case 1 ' Multiply
        r1 = cor1.Red/255.0
        g1 = cor1.Green/255.0
        b1 = cor1.Blue/255.0
        r2 = cor2.Red/255.0
        g2 = cor2.Green/255.0
        b2 = cor2.Blue/255.0
        cor1 = Color.RGB(r1*r2*255,g1*g2*255,b1*b2*255)
        
      Case 2 ' Screen
        r1 = cor1.Red/255.0
        g1 = cor1.Green/255.0
        b1 = cor1.Blue/255.0
        r2 = cor2.Red/255.0
        g2 = cor2.Green/255.0
        b2 = cor2.Blue/255.0
        cor1 = Color.RGB((1.0-(1.0-r1)*(1.0-r2))*255,(1.0-(1.0-g1)*(1.0-g2))*255,(1.0-(1.0-b1)*(1.0-b2))*255)
      end select
      
      ' otherwise, Normal transfer mode
      
    next
    final.RGBSurface.Pixel(x,y) = cor1
  next
next

return final

Is there any way to make it faster?

16

removing the /255.0 * 255
its somehow equivalent 0=0 1=255

create a integer color without .RGB

17

The “Multiply” calculation is usually performed with values between 0 and 1.
But, if I multiply both values (between 0 and 255) and then simply divide by 65025.
This will cut some calculations.
And, what do you mean by " integer color without .RGB"?

18

So, I can assign a color as an Int32?
If yes, that means that I can greatly reduce the calculations.

19

I can assign a color as an Int32?

the docu write this
surf.Pixel(x, y) = &cFFFFFF
https://documentation.xojo.com/api/graphics/rgbsurface.html#rgbsurface-pixel

i guess that each method call to .RGB allocate and free memory that would be in this loop disturbing.

20

But, can I do something like:

surf.Pixel(x, y) = value

where value is an Int32, calculated as (red * 65536)+(green * 256)+blue

???