On Thu, Oct 28, 1999 at 04:45:26PM -0400, Brian S. Julin wrote:
>
> On Thu, 28 Oct 1999 [EMAIL PROTECTED] wrote:
> > I am now converting it to a ggi extension, and I have a few implementation
> > questions:
> >
> > 1) I am currently using a proprietary struc (ggiImg...) which contains
> > width, height, pixelformat, data_layout, and data... would it be better
> > if I used a ggi_visual instead, and just used the in_memory target if I
> > want to do off-screen work, that way they could use the image transforms in
> > a doublebuffer, or offscreen, etc w/o be making a bunch of special cases in
> > my functions...
>
> You can add any extra members you need to add to a visual structure with
> the extension mechanism, so it should be more than possible to use a
> memvisual instead. The tacky part is the way they have to be accessed. From
> within your extension functions, you should have no problem accessing the
> extra structure with a simple macro, but from the application side, the extra
> structure members have to be accessed through a libggiImg API function call. Also,
> what, if any, meaning would there be to Attach()ing ggiImg to a main visual?
>
> > 2) I am making a lot of image tranform functions, should they be in ggiImg, or
> > another extension, as if I use a ggi_visual they would work on any pixel
> > buffer...
>
> I would think transforms and loaders would go nicely together in the same extension.
>
> Another alternative that someone thought up was to make the loaders into
> targets instead of extensions -- but targets that only implement getBox/CrossBlit.
>
> In that case, you would have something like this:
>
> ggi_visual imgvis, memvis, newvis;
> ggi_mode imgmode;
>
> /* display-file-jpeg sets up a visual representing the disk file. */
> imgvis = ggiOpen("display-file-jpeg:/tmp/bootie.jpg");
> ggiGetMode(imgvis, &imgmode);
>
> memvis = ggiOpen("display-memory");
> ggiSetMode(memvis, &imgmode);
>
> /* code in display-file-jpeg target copies data into a memvis */
> ggiCrossBlit(imgvis, 0, 0, imgmode.virt.x, imgmode.virt.y, memvis, 0, 0);
>
> /* Now, to do transforms, we Attach the ggiImg extension. */
> ggiImgAttach(memvis);
>
> /* And say your ggiImg had a function to create a new ggiImg-attached
> visual by shinking an existing one: */
> ggiImgShrink(memvis, 2, 4, &newvis);
>
>
>
>
> Of course, you might want to be able to do it this way, too, if you
> want to reduce memory use by throwing away some data from the disk
> file:
>
>
> ggi_visual imgvis, memvis;
>
> /* display-file-jpeg sets up a visual representing the disk file. */
> imgvis = ggiOpen("display-file-jpeg:/tmp/bootie.jpg");
>
> /* For advanced loading features, Attach the ggiImg extension to the
> display-jpeg and you can get the img-file-jpeg extension sublib. */
> ggiImgAttach(imgvis);
>
> /* Let's say img-file-jpeg has a function to shrink the image while
> loading from disk. */
> ggiImgShrink(imgvis, 2, 4, &memvis);
>
> If you want any help on understanding the extension mechanism, don't hesitate
> to ask; I've written an automatic extension generator in case you weren't
> aware of it.
>
>
>
> P.S. Is anyone answering the webmaster account at ggi-project.org? Please
> check your mail; I need to fix some broken links.
>
> P.P.S. Were some list messages dumped yesterday, or am I just impatient?
>
> --
> Brian
:/ I dont think my last email made it for some reason
I think that an image-loader as a target would work, however it would be less
efficient then:
ggiImgReadPNG(visual, FILE *file, ggi_sint x, y, w, h): This function could in
one step take the image to its destination visual(memory, display, ...),
wheras a target would need to be copied to its destination visual after
loading...
In some cases, where pixelformats agree which happens often, libPNG can write
into a directbuffer of the target visual, which would save memory and some
processing... I have currently implemented the ImgReadPNG for 8 and 16bpp
targets, and image sources, and it wont be too hard to add support for the
other pixelformats...
If I am missing something(I havent made a ggi target before) please tell me...
-Kor Grey <[EMAIL PROTECTED]>
