setPosition method
Set the coordinates of the pixel.
Implementation
@override
void setPosition(int x, int y) {
_x = x;
_y = y;
final bpp = image.numChannels;
_rowOffset = _y * image.rowStride;
_index = _rowOffset + ((_x * bpp) >> 3);
_bitIndex = (_x * bpp) & 0x7;
}