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+---- Thread: Is there a _GETALPHA kind of method? (/showthread.php?tid=2999)
Is there a _GETALPHA kind of method? - Dav - 09-01-2024
I am adding alpha transparency parameter to a SUB using _SETALPHA to change the image, was wondering if there is a way to retrieve current alpha state of that image before I change it, so I can restore it what it was before after calling the SUB.
Thanks!
- Dav
RE: Is there a _GETALPHA kind of method? - SMcNeill - 09-01-2024
_ALPHA32(POINT(x,y))
Note that alpha is stored via pixel and not the whole image.
(Or just _ALPHA, if it's not a 32-bit screen.)
RE: Is there a _GETALPHA kind of method? - Dav - 09-01-2024
Oh cool. That was quick, and is easy. Thanks!
- Dav
RE: Is there a _GETALPHA kind of method? - Dav - 09-02-2024
Yes, that works very well, Steve!
I'm playing around with the original RotoZoom, adding some things, and setting the alpha of the image is one. _SETALPHA calls slows down the SUB, but I would like that option for what I'm using it for. This also has zoom factor apart from the xscale/yscale factor.
In the program you can see the original image alpha being drawn by _PUTIMAGE at the bottom right was restored correctly by the SUB after using it.
EDIT: On second thought, maybe it would just be better to _COPYIMAGE a temp one to use and forget abut having to restore it. Well, at least I know how to do that now.
- Dav
Code: (Select All)
Screen _NewImage(800, 600, 32)
'make an offscreen image to play with
image& = _NewImage(800, 600, 32)
_Dest image&
For o = 1 To 1000
Color _RGB(Rnd * 255, Rnd * 255, Rnd * 255)
Print Rnd;
Next
_Dest 0
Do
Cls , _RGB(255, 255, 255)
RotoZoomy 400, 300, image&, 1 + Sin(zoom), xscale, 1, angle, alpha
RotoZoomy 100, 100, image&, .3, 1, xscale, -angle, 225
RotoZoomy 700, 100, image&, .2, xscale, xscale, angle, 175
RotoZoomy 300, 500, image&, .1, xscale, 1, -angle, 100
Locate 1, 1
Print "Angle :"; CInt(angle)
Print "Zoom :"; Using "##.###"; 1.5 + Sin(zoom)
Print "Alpha :"; alpha
'See im RotoZoomy restored original image alpa info
_PutImage (650, 500)-(800, 600), image&
_Display
_Limit 60
angle = angle + .5: If angle >= 360 Then angle = angle - 360
If fadeway = 0 Then
alpha = alpha + 1: If alpha > 254 Then fadeway = 1
Else
alpha = alpha - 1: If alpha < 1 Then fadeway = 0
End If
If xway = 0 Then
xscale = xscale + .01: If xscale >= 1 Then xway = 1
Else
xscale = xscale - .01: If xscale <= 0 Then xway = 0
End If
zoom = zoom + .01
Loop Until InKey$ <> ""
End
Sub RotoZoomy (x&, y&, image&, zoom, xscale, yscale, angle, alpha)
'Note: this isn't the original RotoZoom
'I'm messing with it as an experiment. (Dav)
_Dest image&
origalpha = _Alpha32(Point(0, 0))
_Dest 0
If alpha < 0 Then alpha = 0
If alpha > 255 Then alpha = 255
_SetAlpha alpha, , image&
w& = _Width(image&): h& = _Height(image&)
Dim px(3) As Single: Dim py(3) As Single
px(0) = -w& / 2: py(0) = -h& / 2 ' Top-left
px(1) = -w& / 2: py(1) = h& / 2 ' Bottom-left
px(2) = w& / 2: py(2) = h& / 2 ' Bottom-right
px(3) = w& / 2: py(3) = -h& / 2 ' Top-right
radianrotation = angle / 57.2957795131
sinr = Sin(-radianrotation): cosr = Cos(-radianrotation)
For i = 0 To 3
x2 = (px(i) * cosr + py(i) * sinr) * zoom * xscale + x&
y2 = (py(i) * cosr - px(i) * sinr) * zoom * yscale + y&
px(i) = x2: py(i) = y2
Next
_MapTriangle _Seamless(0, 0)-(0, h& - 1)-(w& - 1, h& - 1), image& To(px(0), py(0))-(px(1), py(1))-(px(2), py(2))
_MapTriangle _Seamless(0, 0)-(w& - 1, 0)-(w& - 1, h& - 1), image& To(px(0), py(0))-(px(3), py(3))-(px(2), py(2))
'restore alhpa
_SetAlpha origalpha, , image&
End Sub