Rework ROP transparency

Rework ROP behaviour with transparency based upon the results
from roptest.pxl seen on an HP printer.

The old style ROP transparency code used to treat white pixels
as special. The new style code does everything in boolean logic
by modifying the ROP that is used when S or T pixels are set to
be transparent.

This enables us to rip out several cases from the ROP
processing loops, as we never need to check for transparent
pixel values anymore.

1 files changed, 7 insertions, 60 deletions

diff --git a/base/gdevdrop.c b/base/gdevdrop.c
index 82e10fc8c..4d9a1b7b1 100644
--- a/base/gdevdrop.c
+++ b/base/gdevdrop.c
@@ -216,7 +216,8 @@ gx_default_strip_copy_rop2(gx_device * dev,
     pmdev->is_open = true; /* not sure why we need this, but we do. */
     if (code < 0)
         return code;
-    if (rop3_uses_D(gs_transparent_rop(lop))) {
+    lop = lop_sanitize(lop);
+    if (rop3_uses_D(lop)) {
         row = gs_alloc_bytes(mem, draster * block_height, "copy_rop row");
         if (row == 0) {
             code = gs_note_error(gs_error_VMerror);
@@ -651,7 +652,7 @@ mem_default_strip_copy_rop(gx_device * dev,
                            const gx_color_index * tcolors,
                            int x, int y, int width, int height,
                            int phase_x, int phase_y,
-                           gs_logical_operation_t lop)
+                           gs_logical_operation_t olop)
 {
     int depth = dev->color_info.depth;
     int rop_depth = (gx_device_has_color(dev) ? 24 : 8);
@@ -676,10 +677,10 @@ mem_default_strip_copy_rop(gx_device * dev,
     union { long l; void *p; } mdev_storage[20];
     uint row_raster = bitmap_raster(width * depth);
     ulong size_from_mem_device;
-    gs_rop3_t trans_rop = gs_transparent_rop(lop);
-    bool uses_d = rop3_uses_D(trans_rop);
-    bool uses_s = rop3_uses_S(trans_rop);
-    bool uses_t = rop3_uses_T(trans_rop);
+    gs_logical_operation_t lop = lop_sanitize(olop);
+    bool uses_d = rop3_uses_D(lop);
+    bool uses_s = rop3_uses_S(lop);
+    bool uses_t = rop3_uses_T(lop);
     bool expand_s, expand_t;
     byte *row = 0;
     union { long l; void *p; } dest_buffer[16];
@@ -993,60 +994,6 @@ gx_strip_copy_rop_unaligned(gx_device * dev,
 
 /* ---------------- Internal routines ---------------- */
 
-/* Compute the effective RasterOp for the 1-bit case, */
-/* taking transparency into account. */
-gs_rop3_t
-gs_transparent_rop(gs_logical_operation_t lop)
-{
-    gs_rop3_t rop = lop_rop(lop);
-
-    /*
-     * The algorithm for computing an effective RasterOp is presented,
-     * albeit obfuscated, in the H-P PCL5 technical documentation.
-     * Define So ("source opaque") and Po ("pattern opaque") as masks
-     * that have 1-bits precisely where the source or pattern
-     * respectively are not white (transparent).
-     * One applies the original RasterOp to compute an intermediate
-     * result R, and then computes the final result as
-     * (R & M) | (D & ~M) where M depends on transparencies as follows:
-     *      s_tr    p_tr    M
-     *       0       0      1
-     *       0       1      ~So | Po (? Po ?)
-     *       1       0      So
-     *       1       1      So & Po
-     * The s_tr = 0, p_tr = 1 case seems wrong, but it's clearly
-     * specified that way in the "PCL 5 Color Technical Reference
-     * Manual."
-     *
-     * In the 1-bit case, So = ~S and Po = ~P, so we can apply the
-     * above table directly.
-     */
-#define So rop3_not(rop3_S)
-#define Po rop3_not(rop3_T)
-#ifdef TRANSPARENCY_PER_H_P
-/*
- * Believe it or not, MPo depends on S in this case even if the original
- * RasterOp didn't depend on S.
- */
-#  define MPo (rop3_not(So) | Po)
-#else
-#  define MPo Po
-#endif
-    /*
-     * If the operation doesn't use S or T, we must disregard the
-     * corresponding transparency flag.
-     */
-#define source_transparent ((lop & lop_S_transparent) && rop3_uses_S(rop))
-#define pattern_transparent ((lop & lop_T_transparent) && rop3_uses_T(rop))
-    gs_rop3_t mask =
-    (source_transparent ?
-     (pattern_transparent ? So & Po : So) :
-     (pattern_transparent ? MPo : rop3_1));
-
-#undef MPo
-    return (rop & mask) | (rop3_D & ~mask);
-}
-
 typedef enum {
     transform_pixel_region_portrait,
     transform_pixel_region_landscape,