Boost Users :
Subject: Re: [Boost-users] [GIL] rotated90cw_view - jpeg lossless rotation
From: Christian Henning (chhenning_at_[hidden])
Date: 2009-12-06 11:05:27
Hi Jose, please see comments below.
On Sun, Dec 6, 2009 at 5:10 AM, Jose <jmalv04_at_[hidden]> wrote:
> I rotate jpeg photos to portrait by reading the file and saving it like this:
> original size: 4106172 image/jpeg 3264 2448
> rotated size: 5594681 image/jpeg 2448 3264
> The rotation should be lossless (as the image is a multiple of the
> jpeg MCU) but the size has increased significantly and the exif tags
I think libjpeg has a way of applying lossless transformations while
reading it. Is that correct, or am I mistaken here?
How do you preserve the exif tags? Does a user has to read them
separately and cache them?
In the new io extension there is the image_write_info structure which
would allow a user to pass additional information when writing images.
I would be more then willing to add functionality to the new gil::io.
Can you provide a small libjpeg example? I'll also have a look at
> My questions:
> Has it been tested that the rotation is lossless ?
> What can I do make sure the exif tags are preserved ?
Good questions ;-) I'll investigate.
PS: I see there is still one email from you I need to answer. Will do
that later on.
Boost-users list run by williamkempf at hotmail.com, kalb at libertysoft.com, bjorn.karlsson at readsoft.com, gregod at cs.rpi.edu, wekempf at cox.net