openslide_read_region filling buffer with 0's for Mirax

[Terry Wilson]

THANK YOU, I was able to read some non-zero data at that location ... I was
not aware that the data had alpha applied, I just knew black tiles were not
correct.  Is it a reasonable assumption that the alpha value is either 0x00
or 0xff and not some partial values?

Regards,

Terry

On Sun, Apr 12, 2020 at 11:10 PM <jcupitt at gmail.com> wrote:

> I tried and I think it's just because there's no data there. Try:
>
>         openslide_read_region( openslide, data, 20000, 110000, 0, 512, 512
> );
>
> openslide gives you cairo premultiplied ARGB, so 0 means fully
> transparent, ie. the background colour, ie. white. You need to read
> from somewhere with actual data.
>
>
> On Mon, 13 Apr 2020 at 03:40, Terry Wilson <twilson7755 at gmail.com> wrote:
> >
> > Thanks for the zip file ... even using these lib's and dll's, the buffer
> is still being written with all 0's.  If I could ask you one last favor and
> try this very simple program on your windows system and let me know what
> you see.
> >
> > #include "d:\openslide-win64-20171122\include\openslide\openslide.h"
> >
> > int main()
> > {
> >     const char* fn = "C:\\Data\\CMU-3.mrxs";
> >     openslide_t* openslide = openslide_open(fn);
> >
> >     uint32_t *data = new uint32_t[512 * 512];
> >     openslide_read_region(openslide, data, 0, 0, 0, 512, 512);
> >     for (int j = 0; j < 10; ++j)
> >     {
> >         printf("%x,", data[j]);
> >     }
> >
> >     return 0;
> > }
> >
> >
> > Regards,
> >
> > Terry
> >
> > On Sun, Apr 12, 2020 at 6:14 PM <jcupitt at gmail.com> wrote:
> >>
> >> The libvips dev zip has the openslide DLLs and LIBs:
> >>
> >>
> https://github.com/libvips/libvips/releases/download/v8.9.1/vips-dev-w64-all-8.9.1.zip
> >>
> >> On Sun, 12 Apr 2020 at 19:26, Terry Wilson <twilson7755 at gmail.com>
> wrote:
> >> >
> >> > Yes I am able to successfully use your application to open various
> .mrxs files.  Could you send me your libopenslide.lib file to see if I can
> build against your openslide libraries and run successfully?
> >> >
> >> > Thanks,
> >> >
> >> > Terry
> >> >
> >> > On Sun, Apr 12, 2020 at 1:31 PM <jcupitt at gmail.com> wrote:
> >> >>
> >> >> I help maintain an image processing package which includes openslide
> >> >> support. I just tried CMU-3.mrxs in the windows binary and it works
> >> >> for me.
> >> >>
> >> >> Try this:
> >> >>
> >> >>
> https://github.com/libvips/nip2/releases/download/v8.7.0/nip2-8.7.0-setup.zip
> >> >>
> >> >> Unzip and run the .exe to install. To load an MRXS file, click File /
> >> >> Open, navigate to the right directory, select "all files", and
> >> >> double-click on CMU-3.mrxs. It should load as a thumbnail in the
> >> >> workspace. Double-click the thumbnail to open an image view window.
> >> >> You should be able to scroll about and view the file.
> >> >>
> >> >> That's using the standard openslide sources, though I built them
> myself.
> >> >>
> >> >> You can sometimes get problems with special characters or spaces in
> >> >> the folder names, could that be it?
> >> >>
> >> >> John
> >> >> _______________________________________________
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