avfilter/vf_libplacebo: make rotation check more robust

This currently does not make any difference, but it makes the check
more robust against possible future changes to the rotation parameter.

libavfilter/vf_libplacebo.c

@@ -912,8 +912,9 @@ static void update_crops(AVFilterContext *ctx, LibplaceboInput *in,
         image->crop.y0 = av_expr_eval(s->crop_y_pexpr, s->var_values, NULL);
         image->crop.x1 = image->crop.x0 + s->var_values[VAR_CROP_W];
         image->crop.y1 = image->crop.y0 + s->var_values[VAR_CROP_H];
-        image->rotation = s->rotation;
-        if (s->rotation % PL_ROTATION_180 == PL_ROTATION_90) {
+
+        const pl_rotation rot_total = image->rotation - target->rotation;
+        if ((rot_total + PL_ROTATION_360) % PL_ROTATION_180 == PL_ROTATION_90) {
             /* Libplacebo expects the input crop relative to the actual frame
              * dimensions, so un-transpose them here */
             FFSWAP(float, image->crop.x0, image->crop.y0);
@@ -1150,6 +1151,7 @@ static bool map_frame(pl_gpu gpu, pl_tex *tex,
     ));
     out->lut = s->lut;
     out->lut_type = s->lut_type;
+    out->rotation += s->rotation;
 
     if (!s->apply_filmgrain)
         out->film_grain.type = PL_FILM_GRAIN_NONE;