Bug 703161: Fix unknown error when interpolating transparent imagemasks.

Patch from Alex Cherepanov.

Add a dev_spec_op to check for whether copy_alpha is disabled or not.
Clist devices with transparency disable it. Use this to bolster the
decision made in mask_suitable_for_interpolation.

3 files changed, 19 insertions, 3 deletions

diff --git a/base/gxclrect.c b/base/gxclrect.c
index 6f71b61af..d0f81ac4e 100644
--- a/base/gxclrect.c
+++ b/base/gxclrect.c
@@ -599,6 +599,10 @@ clist_dev_spec_op(gx_device *pdev, int dev_spec_op, void *data, int size)
         return 1;
     if (dev_spec_op == gxdso_pattern_shfill_doesnt_need_path)
         return 1;
+    if (dev_spec_op == gxdso_copy_alpha_disabled) {
+        gx_device_clist_writer * const cdev = &((gx_device_clist *)pdev)->writer;
+        return (cdev->disable_mask & clist_disable_copy_alpha) != 0;
+    }
     if (dev_spec_op == gxdso_supports_devn
      || dev_spec_op == gxdso_skip_icc_component_validation) {
         cmm_dev_profile_t *dev_profile;
diff --git a/base/gxdevsop.h b/base/gxdevsop.h
index e2c6a774e..f85724fae 100644
--- a/base/gxdevsop.h
+++ b/base/gxdevsop.h
@@ -29,7 +29,7 @@
  * ioctl is to unix file handles.
  *
  * Design features of this scheme ensure that:
- *  * Devices that support a given call call efficiently implement both
+ *  * Devices that support a given call can efficiently implement both
  *    input and output.
  *  * Devices that do not support a given call can efficiently refuse it
  *    (without having to know all the possible calls).
@@ -401,6 +401,15 @@ enum {
      * for example).
      */
     gxdso_skip_icc_component_validation,
+
+    /* gxdso_copy_alpha_disabled:
+     *     data = NULL
+     *     size = 0
+     * Returns 1 if the command list device sets clist_disable_copy_alpha flag,
+     * 0 otherwise.
+     */
+    gxdso_copy_alpha_disabled,
+
     /* Add new gxdso_ keys above this. */
     gxdso_pattern__LAST
 };
diff --git a/base/gxiscale.c b/base/gxiscale.c
index df0255d74..f175fd22a 100644
--- a/base/gxiscale.c
+++ b/base/gxiscale.c
@@ -145,10 +145,13 @@ static int mask_suitable_for_interpolation(gx_image_enum *penum)
     int code;
     int high_level_color = 1;
 
-    if (gx_device_must_halftone(penum->dev)) {
+    if (gx_device_must_halftone(penum->dev))
         /* We don't interpolate when going to 1bpp outputs */
         return -1;
-    } else if (gx_dc_is_pure(pdc1) && (pdc1)->colors.pure != gx_no_color_index &&
+    if (dev_proc(penum->dev, dev_spec_op)(penum->dev, gxdso_copy_alpha_disabled, NULL, 0) == 1)
+        /* The target device has copy_alpha() disabled. */
+        return -1;
+    if (gx_dc_is_pure(pdc1) && (pdc1)->colors.pure != gx_no_color_index &&
         dev_proc(penum->dev, copy_alpha) != NULL &&
         dev_proc(penum->dev, copy_alpha) != gx_no_copy_alpha) {
         /* We have a 'pure' color, and a valid copy_alpha. We can work with that. */