How can I apply an alpha mask to an Android drawable? -

in application, need change background color of button in response events. works fine setting creating drawable, setting paint , using drawable button background:

    shapedrawable drawable = new shapedrawable(roundrectshape);     drawable.getpaint().setcolor(color);     b.setbackground(drawable); 

now, want overlay alpha mask onto drawable, creating "striped" button. here's how should blue , black button (assuming white background color, these sections should 100% transparent):

i made alpha mask in inkscape, , imported vector asset. might need convert bitmap of sorts, i'm not sure.

i've read bunch of articles , questions mentioning porterduff matrices apply, haven't been able translate these solving current problem.

anyone know how this?

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here's visualization, making things clearer. background color of parent view of button pale pink here, , button border outlined in red (but should invisible in end product):

//this help.

imageview img = (imageview) findviewbyid(r.drawable.yourimage);  img.setalpha(100); 

//transparent between 0 , 255; //if want use bitmap

bitmap b = bitmapfactory.decoderesources(getresources(), r.drawable.yourimage);  img.setimagebitmap(b);  img.setalpha(100);