alpha in 8 bits

BlitzMax Forums/BlitzMax Programming/alpha in 8 bits

Bertrand (Posted 2005) [#1]

I'm surprise to see that the alpha channel use only 1 bit by default. Should be really good to solve that. For example, the TGA Loader module crash when i open picture with alpha.

taxlerendiosk (Posted 2005) [#2]

Er... sorry? Alpha works fine here. Where did you get the 1 bit thing from?

Bertrand (Posted 2005) [#3]

Could you give me an example of creating and visualising alpha in 8 bits please!

ziggy (Posted 2005) [#4]

I think you have the blendmode without alpha. setblend alphabled will use a BYTE to represent the alpha channel instead of a bit.

Bertrand (Posted 2005) [#5]

Well, i have that function: Function Reorder:TPixmap(pixmap:TPixmap, Order:String = "rgba") Local Alp:Byte = 0 Local Red:Byte = 0 Local Gre:Byte = 0 Local Blu:Byte = 0 Local rouge:String Local vert:String Local bleue:String Local mask:String Local re:Int Local ge:Int Local be:Int Local ae:Int Order = Lower(Order) rouge$ = Right(Left(Order,1), 1) If rouge$ = "r" Then re = 16 If rouge$ = "g" Then re = 8 If rouge$ = "b" Then re = 0 If rouge$ = "a" Then re = 24 vert$ = Right(Left(Order ,2), 1) If vert$ = "r" Then ge = 16 If vert$ = "g" Then ge = 8 If vert$ = "b" Then ge = 0 If vert$ = "a" Then ge = 24 bleue$ = Right(Left(Order ,3), 1) If bleue$ = "r" Then be = 16 If bleue$ = "g" Then be = 8 If bleue$ = "b" Then be = 0 If bleue$ = "a" Then be = 24 mask$ = Right(Left(Order ,4), 1) If mask$ = "r" Then ae = 16 If mask$ = "g" Then ae = 8 If mask$ = "b" Then ae = 0 If mask$ = "a" Then ae = 24 Local x:Int Local y:Int Local argb:Int Local out:TPixmap=CreatePixmap( pixmap.width, pixmap.height, pixmap.format ) For x = 0 To PixmapWidth(pixmap)-1 For y = 0 To PixmapHeight(pixmap)-1 argb = ReadPixel(pixmap, x, y) Alp = (argb Shr ae ) & $FF Red = (argb Shr re ) & $FF Gre = (argb Shr ge ) & $FF Blu = (argb Shr be ) & $FF argb = (Alp Shl 24) + (Red Shl 16) + (Gre Shl 8) + (Blu) WritePixel(out, x, y, argb) Next Next Return out End Function When i reorganize the RGB channels, it work perfectly. But when i copy one of RGB channel in the Alpha, i get a binary channel, Please, tell me my mistake?