canvas - Android Use finger to erase bitmap transparency and match background -


scenario:

  1. use fingerpaint example basis
  2. draw text fingerpaint region
  3. want user able erase part of text finger dragging on it

reference: how erase paint finger

tries:

it gets want, src , clear dragging path black. prefer dragging path color drawn canvas without redrawing entire canvas finger moves.

if know fingerpaint this:

canvas.drawcolor(0xffaaaaaa);

i wrote black colored text on top of canvas via drawtext.
tried following combos allow user erase text: 

mpaint.setcolor(0xffaaaaaa); mpaint.setxfermode(new porterduffxfermode(porterduff.mode.clear));  mpaint.setcolor(color.transparent); mpaint.setxfermode(new porterduffxfermode(porterduff.mode.clear));  mpaint.setcolor(0x00aaaaaa); mpaint.setxfermode(new porterduffxfermode(porterduff.mode.clear));

you can multiply 3 out substituting clear mode src mode , showed same result.

question:

anyone know how can make erasure drawpath take appropriate action of erasing part of bitmap dragged on , while doing path being dragged should match color drawn canvas underneath text?


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