You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
96 lines
3.6 KiB
96 lines
3.6 KiB
|
|
---------------------------------------------------------------------------
|
|
WHAT'S DIMG FRAMEWORK ?
|
|
|
|
|
|
Original post from Renchi Raju on digiKam mailing list :
|
|
|
|
[Digikam-devel] Imaging Library
|
|
Renchi Raju renchi at pooh.tam.uiuc.edu
|
|
Sun Jun 19 23:15:20 CEST 2005
|
|
|
|
as you all know, we have been using imlib2 library for the 0.7 series. we
|
|
have had a fairly large number of bugreports because of imlib2 (not
|
|
imlib2's fault, but because of tdelibs's handling of ltdl). In addition,
|
|
some imlib2 bugreports I reported to upstream have gone unfixed for long
|
|
time now.
|
|
|
|
Also, we need to think about 16bit imaging support. this won't come from
|
|
imlib2 and neither from tqt. with qt4 there was hope of 16bit image
|
|
support, but trolltech has made it clear that imaging apps forms only 0.1%
|
|
of their customer base and they are not interested in providing custom
|
|
support for them. so the only solution I see (without depending on
|
|
imagemagick) is to roll our own library.
|
|
|
|
i have been working on a imaging library for digikam, its called DImg.
|
|
it doesn't aim to be a complete imaging library; it uses TQImage for
|
|
rendering and for loading files which are not supported natively by it.
|
|
some of the working/planned features:
|
|
|
|
* Native Image Loaders, for some imageformats which are of interest to
|
|
us: JPEG (complete), TIFF (a rudimentary one currently), PNG (planned), PPM
|
|
(planned). for the rest tqt's qimage is used.
|
|
|
|
* Metadata preservation: when a file is loaded, its metadata like XMP,
|
|
IPTC, EXIF, JFIF are read and held in memory. now when you save back the
|
|
file to the original file or to a different file, the metadata is
|
|
automatically written (How, we have been handling it currently with
|
|
imlib2 is on saving a file: we save the file to a temporary file, reread
|
|
the exif info from the original file and then write to a second temporary
|
|
file.)
|
|
|
|
* Explicitly Shared Container format (see tqt docs): this is necessary for
|
|
performance reasons.
|
|
|
|
* 8bit and 16bit support: if the file format is 16 bit, it will load up
|
|
the image in 16bit format (currently only 16bit tiff support) and all
|
|
operations are done in 16 bit format, except when the rendering to screen
|
|
is done, when its converted on the fly to a temporary 8bit image and then
|
|
rendered.
|
|
|
|
* Basic image manipulation: rotate, flip, color modifications, crop,
|
|
scale (this has been ported from Imlib2 - originally ported by Mosfet, I
|
|
added 16 bit scaling support and support for scaling of only a section of
|
|
the image)
|
|
|
|
* Rendering to Pixmap: using TQImage/QPixmap. (see above for rendering of
|
|
16bit images).
|
|
|
|
* Pixel format: the pixel format is different from TQImage/Imlib2 pixel
|
|
format. In TQImage/Imlib2 the pixel data is stored as unsigned ints and to
|
|
access the individual colors you need to use bit-shifting to ensure
|
|
endian correctness. in DImg, the pixel data is stored as unsigned char.
|
|
the color layout is B,G,R,A (blue, green, red, alpha)
|
|
|
|
for 8bit images: you can access individual color components like this:
|
|
|
|
uchar* pixels = image.bits();
|
|
for (int i=0; i<image.width()*image.height(); i++)
|
|
{
|
|
pixel[0] // blue
|
|
pixel[1] // green
|
|
pixel[2] // red
|
|
pixel[3] // alpha
|
|
|
|
pixel += 4; // go to next pixel
|
|
}
|
|
|
|
and for 16bit images:
|
|
|
|
ushort* pixels = (ushort*)image.bits();
|
|
for (int i=0; i<image.width()*image.height(); i++)
|
|
{
|
|
pixel[0] // blue
|
|
pixel[1] // green
|
|
pixel[2] // red
|
|
pixel[3] // alpha
|
|
|
|
pixel += 4; // go to next pixel
|
|
}
|
|
|
|
the above is true for both big and little endian platforms. What this also
|
|
means is that the pixel format is different from that of TQImage for big
|
|
endian machines. Functions are provided if you want to get a copy of the
|
|
DImg as a TQImage.
|
|
|