opencv - Mat::convertto() not working in javacv, android camera -

i developing android opencv app based on opencv4android sdk tutorial 2 - mixed processing.

in frame processing function public mat oncameraframe(cvcameraviewframe inputframe) {}

the frame rgba , want make rgb doing this:

 mrgba = inputframe.rgba();  mgray = inputframe.gray();   mat    mrgb=new mat(640,480,cvtype.cv_8uc3);  mrgba.convertto(mrgb, cvtype.cv_8uc3);  //imgproc.cvtcolor(mrgba, mrgb, cvtype.cv_8uc3);  pinkimage(mrgb.dataaddr()); 

but when debug , log things passed jni part, find it's not working @ all. mrgb cv_8uc4 after calling converto()

what cause of this?

ok, answer here

imgproc.cvtcolor(mrgba,mrgb,imgproc.color_rgba2rgb); 

instead of

mrgba.convertto(mrgb, cvtype.cv_8uc3); 

thanks lot!!