STEP_C2           824 3rdparty/libjpeg/jquant2.c     inc2 = inc2 * (2 * STEP_C2) + STEP_C2 * STEP_C2;
STEP_C2           841 3rdparty/libjpeg/jquant2.c           xx2 += 2 * STEP_C2 * STEP_C2;