Bug 689521

Summary:	-dDOINTERPOLATE does not override image dictionary
Product:	Ghostscript	Reporter:	Ralph Giles <ralph.giles>
Component:	PDF Interpreter	Assignee:	Alex Cherepanov <alex>
Status:	RESOLVED DUPLICATE
Severity:	normal	Keywords:	bountiable
Priority:	P4
Version:	master
Hardware:	PC
OS:	Linux
Customer:		Word Size:	---

Description Ralph Giles 2007-10-16 15:29:55 UTC

My understanding from Ray is that -dDOINTERPOLATE is that should turn on
interpolation for all images. The documentation in Use.htm concurs.

However, running PLANHALF.pdf from Bug 688869, a combination of DCT, CCITTFax
and JPX images, I only see it enter the image interpolation code at all for 1
bpc images.

$ bin/gs -sDEVICE=pbmraw -o foo.pbm -r36 -dDOINTERPOLATE PLANHALF.pdf 

It would be nice for display quality if other image depths were scaled down with
an intelligent filter.

Comment 1 Alex Cherepanov 2007-10-20 21:06:44 UTC

Interpolation is implemented in a device-dependent way and 1 bpc images
are handled separately from other cases.

Checking the interpolation parameter in data_image_params() shows that it
is always on when -dDOINTERPOLATE is defined. However, Ghostscript can currently
interpolate only non-skewed images at 0 and 180 deg. rotation. Most images
in the sample file are skewed or rotated.

The PDF interpreter and PS code work fine. At most, this is an enhancement
request for the rendering logic.

Comment 2 Ray Johnston 2007-10-23 09:26:14 UTC

Alex is the owner Image and filter stuff.

Comment 3 Alex Cherepanov 2009-01-21 14:33:07 UTC

Mark an early but user-priority bug a duplicate of newer customer
priority bug.


*** This bug has been marked as a duplicate of 690246 ***