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On 05/10/2012 04:48 PM, Petr Kitashov wrote:
<blockquote
cite="mid:CAP9804+gk2dtwnTLpMoTVy1E45Ta8PDc4-EraczmCqz_P6JGDQ@mail.gmail.com"
type="cite"><span style="">Hi,</span><br style="">
<br style="">
<span style="">I need just to display some region(any) from raster
file. </span><span style="">Seems like I understand everything
until rasterIO.</span><br style="">
<span style="">RasterIO fills(in my case) void* pData with raster
info - </span><span style="">that's great, but how to display
it?</span><br style="">
</blockquote>
<br>
I do it like this:<br>
<br>
1) Call GDALRasterIO to get the part of interest into a 2D table of
floats or integers (ral_grid).<br>
<br>
This happens in ral_grid_create_using_GDAL in
<a class="moz-txt-link-freetext" href="https://github.com/ajolma/geoinformatica/blob/master/libral/ral_grid_rw.c">https://github.com/ajolma/geoinformatica/blob/master/libral/ral_grid_rw.c</a><br>
<br>
2) Create a ral_pixbuf (each pixel has RGBA values) of the same size
as ral_grid.<br>
<br>
3) Render the ral_grid onto the ral_pixbuf using current palette etc.<br>
<br>
4) Convert the ral_pixbuf into GdkPixBuf.<br>
<br>
5) Use the GdkPixBuf in a GTK+ image widget for display.<br>
<br>
This happens in ral_pixbuf_create_from_grid,
ral_render_integer_grid, and ral_gdk_pixbuf in
<a class="moz-txt-link-freetext" href="https://github.com/ajolma/geoinformatica/blob/master/libral/ral_pixbuf.c">https://github.com/ajolma/geoinformatica/blob/master/libral/ral_pixbuf.c</a><br>
<br>
This is GTK+ specific. There are other Graphics toolkits.<br>
<br>
<blockquote
cite="mid:CAP9804+gk2dtwnTLpMoTVy1E45Ta8PDc4-EraczmCqz_P6JGDQ@mail.gmail.com"
type="cite">
<br style="">
<span style="">Which data is stored there when I use
GDALDataset::rasterIO, </span><span style="">and which in case
of GDALRasterBand::RasterIO?</span><br style="">
<br style="">
<span style="">I.e. how to determine pixel values from pData?</span><br
style="">
<br style="">
<span style="">I'm sorry if this question is stupid, but i spent a
lot of time in google and </span><span style="">didn't find any
solution.</span> <br clear="all">
</blockquote>
<br>
I hope the above helps.<br>
<br>
Ari<br>
<br>
<blockquote
cite="mid:CAP9804+gk2dtwnTLpMoTVy1E45Ta8PDc4-EraczmCqz_P6JGDQ@mail.gmail.com"
type="cite">
<div><br>
</div>
-- <br>
Best Regards, <br>
Petr Kitashov
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
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</blockquote>
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