Bug 706373: Improve detection of image clipping.

When we set out to render an image, we calculate the target
rectangle. We attempt to reduce this according to the
clip path as much as we can so as to limit the amount of
excess work we do - particularly for interpolated images.

Unfortunately, in some cases (including some clist cases) this
code is called without a clip path in place, and so we were
failing to clip the target at all. This meant that for images
that spanned the whole page, we could end up interpolating the
whole image for every single band.

Here, we adapt the code so that in the absence of a clip path
we use the bbox of the target device as bounds.

1 files changed, 19 insertions, 8 deletions

diff --git a/base/gxipixel.c b/base/gxipixel.c
index 26b4d7667..672c935fd 100644
--- a/base/gxipixel.c
+++ b/base/gxipixel.c
@@ -432,23 +432,33 @@ gx_image_enum_begin(gx_device * dev, const gs_gstate * pgs,
     }
 
     /* Can we restrict the amount of image we need? */
-    while (pcpath && !pim->imagematrices_are_untrustworthy) /* So we can break out of it */
+    while (!pim->imagematrices_are_untrustworthy) /* So we can break out of it */
     {
         gs_rect rect, rect_src;
         gs_matrix mi;
         const gs_matrix *m = pgs != NULL ? &ctm_only(pgs) : NULL;
-        gs_fixed_rect obox;
         gs_int_rect irect;
         if (m == NULL || (code = gs_matrix_invert(m, &mi)) < 0 ||
             (code = gs_matrix_multiply(&mi, &pic->ImageMatrix, &mi)) < 0) {
             /* Give up trying to shrink the render box, but continue processing */
             break;
         }
-        gx_cpath_outer_box(pcpath, &obox);
-        rect.p.x = fixed2float(obox.p.x);
-        rect.p.y = fixed2float(obox.p.y);
-        rect.q.x = fixed2float(obox.q.x);
-        rect.q.y = fixed2float(obox.q.y);
+        if (pcpath)
+        {
+            gs_fixed_rect obox;
+            gx_cpath_outer_box(pcpath, &obox);
+            rect.p.x = fixed2float(obox.p.x);
+            rect.p.y = fixed2float(obox.p.y);
+            rect.q.x = fixed2float(obox.q.x);
+            rect.q.y = fixed2float(obox.q.y);
+        }
+        else
+        {
+            rect.p.x = 0;
+            rect.p.y = 0;
+            rect.q.x = dev->width;
+            rect.q.y = dev->height;
+        }
         /* rect is in destination space. Calculate rect_src, in source space. */
         code = gs_bbox_transform(&rect, &mi, &rect_src);
         if (code < 0) {
@@ -460,6 +470,7 @@ gx_image_enum_begin(gx_device * dev, const gs_gstate * pgs,
         /* If mi.{xx,yy} > 1 then we are downscaling. During downscaling,
          * the support increases to ensure that we don't lose pixels contributions
          * entirely. */
+        if (pim->Interpolate)
         {
             float support = any_abs(mi.xx);
             int isupport;
@@ -479,7 +490,7 @@ gx_image_enum_begin(gx_device * dev, const gs_gstate * pgs,
             rect_src.p.x -= isupport;
             rect_src.p.y -= isupport;
             rect_src.q.x += isupport;
-            rect_src.q.y += isupport;
+            rect_src.q.y += isupport+1; /* +1 is a fudge! */
         }
         irect.p.x = (int)floor(rect_src.p.x);
         irect.p.y = (int)floor(rect_src.p.y);