HP L 5 manual ROPs in the RGB Color Space

For example, the logic equation for ROP 252 in the RGB color space is T OR S, which is shown as TSo in Table 5-4. The truth table for the ROP is shown above, and can be seen to correspond to the logic equation TSo, that is, D gets the value of T OR S without regard to the current value of D. Furthermore, the binary value of 252 is 11111100 and corresponds with the value of the D for all the combinations of T and S, when the truth table starts with (1, 1, 1) and ends with (0, 0, 0).

It’s possible to derive the logical operation for a truth table and to create a truth table for a logical operation. However, the most important point is that the binary value of the ROPs number gives the Destination for all possible combinations of Texture, Source, and Destination.

The way the bits of the ROPs number map to the combinations of Texture, Source, and Destination depends on whether the color space is RGB or CMY. The least significant bit of the RGB ROP value maps to (0, 0, 0), the color black in RGB, and the most significant bit to (1, 1, 1), white in RGB. On the other hand, the CMY ROP reverses the mapping. This reversal hinges on the fact that RGB and CMY are the inverse of each other, i.e., RGB Black is (0, 0, 0) and CMY Black is (1, 1, 1), white. All other colors show the same relationship.

ROPs in the RGB Color Space

The RGB ROP truth tables shown in Table 5-1 illustrate how ROP 252 and ROP 90 work, and most importantly how the bits in the ROP map show destination values for each combination of Texture, Source and Destination. A “1” in the RGB color space represents white and a “0” black, which makes determining what shows on paper cumbersome for users since the paper is marked when the Destination has a “0” value.

5-14 The PCL Print Model EN