GeUserArea use DrawBitmap() to overlay multiple images(has alpha)

[chuanzhen]

Hi
I drew some images in UserArea use DrawBitmap(), but when I overlaid the images, the alpha of the final drawn image was not transparent, but the color of DrawSetPen() was used. How can I make the transparent area of the overlaid image display the color of the lower layer.

my code :

self.DrawSetPen(c4d.Vector(0))
self.DrawBitmap(dragbmp,x, y, width, height,  0, 0, width, height, c4d.BMP_ALLOWALPHA)

This is an example of a video where when I drag the image, the transparent area of the image turns black and the background color is not displayed:

Thanks for any help!

[chuanzhen]

I found a solution in other posts, and this is an video example:

example code:

import c4d

from c4d import bitmaps,gui





class DraggingArea(c4d.gui.GeUserArea):
    def __init__(self):
        self.startx = 0
        self.starty = 0

    def DrawMsg(self, x1, y1, x2, y2, msg):


        # Initializes draw region
        self.OffScreenOn()
        self.SetClippingRegion(x1, y1, x2, y2)
        icon_bmp = bitmaps.InitResourceBitmap(5159)
        icon_clip = bitmaps.GeClipMap()
        icon_clip.InitWithBitmap(icon_bmp,icon_bmp.GetInternalChannel())

        clip = bitmaps.GeClipMap()
        w,h = self.GetWidth(),self.GetHeight()
        clip.Init(w,h)
        clip.BeginDraw()
        clip.SetColor(0,0,180)
        clip.FillRect(0,0,w,int(h*0.4))
        clip.SetColor(180,0,0)
        clip.FillRect(0,int(h*0.4),w,h)

        clip.SetDrawMode(c4d.GE_CM_DRAWMODE_BLEND,255)
        clip.Blit(self.startx,self.starty,icon_clip,0,0,icon_clip.GetBw(),icon_clip.GetBh(),c4d.GE_CM_BLIT_COL)


        clip.EndDraw()
        # Get default Background color
        bmp = clip.GetBitmap()
        self.DrawBitmap(bmp,0,0,w,h,0,0,w,h,c4d.BMP_NORMAL)




    def InputEvent(self, msg):
        """
        Called by Cinema 4D, when there is a user interaction (click) on the GeUserArea.
        This is the place to catch and handle drag interaction.

        :param msg: The event container.
        :type msg: c4d.BaseContainer
        :return: True if the event was handled, otherwise False.
        :rtype: bool
        """
        # Do nothing if its not a left mouse click event
        if msg[c4d.BFM_INPUT_DEVICE] != c4d.BFM_INPUT_MOUSE and msg[c4d.BFM_INPUT_CHANNEL] != c4d.BFM_INPUT_MOUSELEFT:
            return True

        # Retrieves the initial position of the click
        mouseX = msg[c4d.BFM_INPUT_X]
        mouseY = msg[c4d.BFM_INPUT_Y]
        mouse_pos_dict = self.Global2Local()
        x, y = mouse_pos_dict['x'] + msg.GetInt32(c4d.BFM_INPUT_X), mouse_pos_dict['y'] + msg.GetInt32(
            c4d.BFM_INPUT_Y)  
        self.startx = x
        self.starty = y

        # Initializes the start of the dragging process (needs to be initialized with the original mouseX, mouseY).
        self.MouseDragStart(c4d.KEY_MLEFT, mouseX, mouseY, c4d.MOUSEDRAGFLAGS_DONTHIDEMOUSE | c4d.MOUSEDRAGFLAGS_NOMOVE)
        isFirstTick = True

        # MouseDrag needs to be called all time to update information about the current drag process.
        # This allow to catch when the mouse is released and leave the infinite loop.
        while True:

            # Updates the current mouse information
            result, deltaX, deltaY, channels = self.MouseDrag()
            if result != c4d.MOUSEDRAGRESULT_CONTINUE:
                break

            # The first tick is ignored as deltaX/Y include the mouse clicking behavior with a deltaX/Y always equal to 4.0.
            # However it can be useful to do some initialization or even trigger single click event
            if isFirstTick:
                isFirstTick = False
                continue

            # If the mouse didn't move, don't need to do anything
            if deltaX == 0.0 and deltaY == 0.0:
                continue

            # Updates mouse position with the updated delta
            mouseX -= deltaX
            mouseY -= deltaY
            x -= deltaX
            y -= deltaY
            self.startx = int(x)
            self.starty = int(y)




            # Redraw the GeUserArea (it will call DrawMsg)
            self.Redraw()

        # Asks why we leave the while loop
        endState = self.MouseDragEnd()



        return True


class MyDialog(c4d.gui.GeDialog):
    """
    Creates a Dialog with only a GeUserArea within.
    """

    def __init__(self):
        # It's important to stores our Python implementation instance of the GeUserArea in class variable,
        # This way we are sure the GeUserArea instance live as long as the GeDialog.
        self.area = DraggingArea()

    def CreateLayout(self):
        """
        This method is called automatically when Cinema 4D Create the Layout (display) of the Dialog.
        """
        self.AddUserArea(1000, c4d.BFH_SCALEFIT | c4d.BFV_SCALEFIT)
        self.AttachUserArea(self.area, 1000)
        return True


def main():
    # Creates a new dialog
    dialog = MyDialog()

    # Opens it
    dialog.Open(dlgtype=c4d.DLG_TYPE_MODAL_RESIZEABLE, defaultw=500, defaulth=500)


if __name__ == '__main__':
    main()