FloodFill with alpha mask

General
1

Recently, I have been trying to think of a way of using the RGBSurface and pictures to FloodFill a fully transparent area. The RGBSurface only supports a depth of 32 and I was wondering if there was an easy way to get FloodFill to fill transparent areas.

I thought about FloodFilling the alpha mask but I cannot think how I could avoid pixel-by-pixel processing through Xojo code to get it to fill the colour on the actual image rather than the mask.

Thanks

2

Make a new picture the same size as the original and filled with the color you want. Copy the mask from the original and invert it (see transform for more info). Set the mask of the new image to the inverted mask. Then draw the new image on top of the old one.

3

Interesting approach. I will try it.

Thanks

4

What are you referring to with ‘see transform’? I do not know what the best approach is for inverting a mask.

Thanks

5

http://documentation.xojo.com/index.php/RGBSurface.Transform

6

Thanks

7

How do I pass the map in? Thanks

8

The example on that page shows how to do that.

9

Ah…I think I understand it now.

Thanks!

10

I have attempted this but it does not seem to make a difference to the picture.

Sub Fill(x as integer, y as integer, col as Color)
  //if pixel is partially or fully opaque
  if ImageCanvas1.Image.Mask.RGBSurface.Pixel(x, y) <> &cFFFFFF  then
    ImageCanvas1.Image.RGBSurface.FloodFill(x, y, col)
  else
    //fill image with desired colour
    dim p1 as new picture(ImageCanvas1.Image.Width, ImageCanvas1.Image.Height)
    p1.Graphics.ForeColor = col
    p1.Graphics.FillRect(0, 0, p1.width, p1.height)
     //apply inverted mask
    dim p2 as picture = ImageCanvas1.Image.Mask.ClonePicture
    ImagePlayEffectsLibrary.Invert(p2)
    p1.ApplyMask(p2)
    //draw new image over original
    ImageCanvas1.Image.Graphics.DrawPicture(p1, 0, 0)
  end if
  Invalidate(false)
End Sub

Thanks!

11

BUMP. someone please help me. Has anybody done a similar method to this?

Thanks

12

Just follow the steps Greg pointed out:

  ' draw the unmasked original picture on the result picture
  dim ResultPic as new Picture(320,240,32)
  ResultPic.Graphics.DrawPicture origPic,0,0
  
  ' build the masked floodfill picture
  dim FFPic as new Picture(320,240,32)
  FFPic.Graphics.DrawPicture FloodfillMask,0,0
  ' and on the mask of the floodfill picture
  FFPic.Mask.Graphics.DrawPicture FloodfillMask,0,0
  
  ' floodfill on this newly build floodfill picture
  FFPic.RGBSurface.FloodFill 160,120, &cFF0000
  
  ' invert mask of floodfilled pic
  Dim map(255) As Integer
  For i As Integer = 0 To 255
    map(i) = 255 - i
  Next
  FFpic.Mask.RGBSurface.Transform(map)
  
  ' draw floodfilled picture on result picture
  ResultPic.Graphics.DrawPicture FFPic,0,0
13

[quote=114956:@Alain Bailleul]Just follow the steps Greg pointed out:

[code]
’ draw the unmasked original picture on the result picture
dim ResultPic as new Picture(320,240,32)
ResultPic.Graphics.DrawPicture origPic,0,0

’ build the masked floodfill picture
dim FFPic as new Picture(320,240,32)
FFPic.Graphics.DrawPicture FloodfillMask,0,0
’ and on the mask of the floodfill picture
FFPic.Mask.Graphics.DrawPicture FloodfillMask,0,0

’ floodfill on this newly build floodfill picture
FFPic.RGBSurface.FloodFill 160,120, &cFF0000

’ invert mask of floodfilled pic
Dim map(255) As Integer
For i As Integer = 0 To 255
map(i) = 255 - i
Next
FFpic.Mask.RGBSurface.Transform(map)

’ draw floodfilled picture on result picture
ResultPic.Graphics.DrawPicture FFPic,0,0
[/code][/quote]
Thanks. What does Floodfillmask represent? The mask for the original image?

Thanks

14

yes, you use it for both the picture and the mask of FFPic

15

I am sorry. I still have not managed to get this to work. Anybody got any suggestions or can whip up an example from any of your existing projects?

Thanks

16

Both ‘the picture’ - the result picture?

Thanks

18

Here is the code I got. I tried all sorts to get it to work:

Not exactly what I wrote but I changed it so that the method does not require any modules installed into your project. I tested this code anyway and all it seemed to do was invert the image.

Thanks