openslide_read_region returns no picture data

[Stefan König]

i tried it now with this call:

       openslide_read_region(slideObject, dst, 27500, 27500, 0,
*width, *height);

even if i set dimensions to 10000x1000 i get only (big) plane black
pictures, i tried some different mirax files right now, allways the
same thing.

this produces a black image too

2010/12/10 Stefan König <blogdde at googlemail.com>:
> here is a part of my sample script to play bit arround with openslide,
> before i use this productive:
>
>        openslide_read_region(slideObject, dst, 0, 0, 1, *width, *height);
>
>        if(openslide_get_error(slideObject))
>                std::cout << openslide_get_error(slideObject) << std::endl;
>
>        argb8c_view_t gil = boost::gil::interleaved_view(*width, *height,
> (const argb8c_pixel_t*) (dst), (*width)*4);
>
>        rgb8_image_t exp(*width,*height);
>        copy_and_convert_pixels(gil, view(exp));
>
>        jpeg_write_view("C:\\readRegionTest.jpg", view(exp));
>
>        std::cout << "***************************************" << std::endl;
>        std::cout << "finished region read" << std::endl;
>        std::cout << "***************************************" << std::endl;
>
>
>        int64_t* w = new int64_t;
>        int64_t* h = new int64_t;
>        const char* name = openslide_get_associated_image_names(slideObject)[1];
>        openslide_get_associated_image_dimensions (slideObject, name, w, h);
>        uint32_t* dst2 = new uint32_t[(*w)*(*h)*4];
>        openslide_read_associated_image (slideObject, name, dst2);
>
>        if(openslide_get_error(slideObject))
>                std::cout << openslide_get_error(slideObject) << std::endl;
>
>        argb8c_view_t gil2 = boost::gil::interleaved_view(*w, *h, (const
> argb8c_pixel_t*) (dst2), *w*4);
>
>        rgb8_image_t exp2(*w,*h);
>        copy_and_convert_pixels(gil2, view(exp2));
>
>        jpeg_write_view("C:\\readAssociatedRegionTest.jpg", view(exp2));
>
>        std::cout << "***************************************" << std::endl;
>        std::cout << "finished associated region read" << std::endl;
>        std::cout << "***************************************" << std::endl;
>
> this is my output:
>
> the second picture is created successfully, the first one is only
> black (the dst pointer is empty.), i executed this script by using the
> mirax sample files from the openslide project page.
>
> ***************************************
> ***************************************
> finished region read
> ***************************************
> ***************************************
> finished associated region read
> ***************************************
>
>
> 2010/12/8 Stefan König <blogdde at googlemail.com>:
>> The error state is empty and a read_associated_image call works fine aber
>> calling read_region.
>>
>> I debugged inside the read_region code, I think there is something wrong
>> with some of the cairo calls painting to the buffer, but there is no proof
>> yet.
>>
>> Friday I'll take a further look, and I'll write here if I find something.
>>
>>
>> -----Ursprüngliche Nachricht-----
>> Von: openslide-users-bounces+blogdde=googlemail.com at lists.andrew.cmu.edu
>> [mailto:openslide-users-bounces+blogdde=googlemail.com at lists.andrew.cmu.edu]
>> Im Auftrag von Jan Harkes
>> Gesendet: Mittwoch, 8. Dezember 2010 17:13
>> An: openslide-users at lists.andrew.cmu.edu
>> Betreff: Re: openslide_read_region returns no picture data
>>
>> On 12/08/2010 10:21 AM, Stefan König wrote:
>>> Hi,
>>>
>>> i try to read a single region out of mirax file (just tried my own and
>>> the sample files from openslide.org), if i use
>>> openslide_get_associated_image_dimensions() i can extract my image and
>>> save work with them but if i try to extract a image by using
>>> openslide_read_region my dst pointer contains nothing and there is no
>>> exception either :(
>>>
>>>       *width = 256;
>>>       *height = 256;
>>>
>>>       uint32_t* dst = new uint32_t[(*width)*(*height)*4];
>>>       openslide_read_region(slideObject, dst, 0, 0, 1, *width, *height);
>>>
>>> if i understand the documentation right, it should take my slide
>>> object and write a 256x256 area begining at topleft from layer to dst?
>>
>> I believe that that should work. But it may be that the slideObject
>> handle got into an error state, you probably should check for errors by
>> calling 'openslide_get_error' after the call to openslide_read_region
>> and probably most other calls.
>>
>> According to the C api documentation, when the object is in error state
>> openslide_read_region will clear the dst buffer instead of painting to it.
>>
>> Jan
>>
>> _______________________________________________
>> openslide-users mailing list
>> openslide-users at lists.andrew.cmu.edu
>> https://lists.andrew.cmu.edu/mailman/listinfo/openslide-users
>>
>>
>