Is there a _GETALPHA kind of method?

[Dav]

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

[SMcNeill]

_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.)

[Dav]

Oh cool.  That was quick, and is easy.  Thanks!

- Dav

[Dav]

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