Android OpenGL ES 1.1 - 2D Texture Scribbling

1) OpenGL ES 1.1 for Android 2) Scribble with 2D Texture using touch event 3) Overlapped textures should produce smooth lines 4) There should not be any black overlap border on textures. 5) Background should be transparent 6) Minimum 20fps refresh rate with full screen scribbling 7) Development in NDK is optional. Attached is a sample 2D texture bitmap. Attached screenshot shows how scribble should look except there are two issues - scribble lines are not smooth and overlapping areas has black borders.