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Zach,
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<div class="">If I’m understanding your question correctly, MapServer will always give you your requested coordinate space inside of the requested image size, by buffering the image results along the axis that is larger than the coordinate window needs to draw
completely. In other words, MapServer automatically pads the output image to fill in those areas, East/West and North/South edges based on the coordinate space requested.</div>
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<div class="">If you need them to match up exactly, then you need to do the computations in your application to make the correct requests and make the coordinate window ratio match the pixel window (image size) ratios.</div>
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<div class="">bobb</div>
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<div class="">On Oct 1, 2015, at 2:13 PM, Zach Chehayeb <<a href="mailto:zach.chehayeb@airborne.aero" class="">zach.chehayeb@airborne.aero</a>> wrote:</div>
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Hello All,<o:p class=""></o:p></div>
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<o:p class=""> </o:p></div>
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Can anyone explain or point me in the right direction on how mapserver logic works when a requested map extent cannot be produced at the requested resolution with square pixels?<o:p class=""></o:p></div>
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<o:p class=""> </o:p></div>
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I am using mapserver in an application that requests mapserver to produce various map extents at various resolutions. The map config is set to not allow non square pixel (so the MS_NONSQUARE setting is set to no). The application currently assumes that the
extent height should always be half of the width. Of course, with MS_NONSQUARE set to no and producing resolutions where the height is not always exactly half of the width, mapserver is unable to produce the exact extents requested. As such, mapserver compensates
by extending either the north and south or east and west bounds of the map. See images in link below for a detailed illustration (the red box indicates the requested extent). For all images below, the requested extent is x1=-58.615527, y1=50.434875, x2=-13.615527,
y2=72.934875, but the actual extents differ.<o:p class=""></o:p></div>
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<o:p class=""> </o:p></div>
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From my observations, it seems that there are three cases. I have included a link below where a zip file that has examples of the cases can be downloaded.<o:p class=""></o:p></div>
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<a href="https://www.dropbox.com/s/dy1cgmt8lmbl3wf/Example%20Images.zip?dl=0" style="color: purple; text-decoration: underline;" class="">https://www.dropbox.com/s/dy1cgmt8lmbl3wf/Example%20Images.zip?dl=0</a><o:p class=""></o:p></div>
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<span class="">1.<span style="font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-family: 'Times New Roman';" class=""> <span class="Apple-converted-space"> </span></span></span>The requested resolution
height is greater than half of the width (1280x720).<o:p class=""></o:p></div>
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<span class="">a.<span style="font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-family: 'Times New Roman';" class=""> <span class="Apple-converted-space"> </span></span></span>Result: MapServer locks
on the East and West bounds and extends the North and South bounds of the map.<o:p class=""></o:p></div>
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<span class="">2.<span style="font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-family: 'Times New Roman';" class=""> <span class="Apple-converted-space"> </span></span></span>The requested resolution
height is less than half of the width (960x400).<o:p class=""></o:p></div>
<div style="margin: 0in 0in 0.0001pt 1in; font-size: 11pt; font-family: Calibri, sans-serif; text-indent: -0.25in;" class="">
<span class="">a.<span style="font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-family: 'Times New Roman';" class=""> <span class="Apple-converted-space"> </span></span></span>Result: MapServer locks
on the North and South bounds and extends the East and West bounds.<o:p class=""></o:p></div>
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<span class="">3.<span style="font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-family: 'Times New Roman';" class=""> <span class="Apple-converted-space"> </span></span></span>The requested resolution
height is half of the width (1000x500).<o:p class=""></o:p></div>
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<span class="">a.<span style="font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-family: 'Times New Roman';" class=""> <span class="Apple-converted-space"> </span></span></span>Result: MapServer produces
the image at the requested resolution.<o:p class=""></o:p></div>
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<o:p class=""> </o:p></div>
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Is anyone able to confirm that these are the only three cases or correct my understanding (if there is more to it than I have described)?<o:p class=""></o:p></div>
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<o:p class=""> </o:p></div>
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Some info about my installation:<o:p class=""></o:p></div>
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<span class="">1.<span style="font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-family: 'Times New Roman';" class=""> <span class="Apple-converted-space"> </span></span></span>MapServer version 6.0.3
OUTPUT=GIF OUTPUT=PNG OUTPUT=JPEG SUPPORTS=PROJ SUPPORTS=AGG SUPPORTS=FREETYPE SUPPORTS=ICONV SUPPORTS=FRIBIDI SUPPORTS=WMS_SERVER SUPPORTS=WMS_CLIENT SUPPORTS=WFS_SERVER SUPPORTS=WFS_CLIENT SUPPORTS=FASTCGI SUPPORTS=THREADS INPUT=OGR INPUT=GDAL INPUT=SHAPEFILE<o:p class=""></o:p></div>
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<o:p class=""> </o:p></div>
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Please let me know if there is any other information needed.<o:p class=""></o:p></div>
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<o:p class=""> </o:p></div>
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Thanks in advance,<o:p class=""></o:p></div>
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<o:p class=""> </o:p></div>
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<span style="" class="">Zach Chehayeb<o:p class=""></o:p></span></div>
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<span style="" class="">Application Developer<o:p class=""></o:p></span></div>
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<span style="" class="">Email.</span><span style="color: rgb(31, 73, 125);" class=""> </span><a href="mailto:zach.chehayeb@airborne.aero" style="color: purple; text-decoration: underline;" class="">zach.chehayeb@airborne.aero</a><span style="color: rgb(31, 73, 125);" class=""><o:p class=""></o:p></span></div>
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<span style="" class="">Tel No. +1 949 707 1800<o:p class=""></o:p></span></div>
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<a href="x-msg://46/www.airborne.aero" style="color: purple; text-decoration: underline;" class="">www.airborne.aero</a><span style="color: rgb(31, 73, 125);" class=""><o:p class=""></o:p></span></div>
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<span style="color: rgb(31, 73, 125);" class=""> </span></div>
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<span style="color: rgb(31, 73, 125);" class=""><image001.jpg></span><span style="font-family: Arial, sans-serif;" class=""><o:p class=""></o:p></span></div>
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<o:p class=""> </o:p></div>
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<o:p class=""> </o:p></div>
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<o:p class=""> </o:p></div>
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<o:p class=""> </o:p></div>
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<span style="font-family: ComicSansMS; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">_______________________________________________</span><br style="font-family: ComicSansMS; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: ComicSansMS; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">mapserver-users
mailing list</span><br style="font-family: ComicSansMS; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<a href="mailto:mapserver-users@lists.osgeo.org" style="color: purple; text-decoration: underline; font-family: ComicSansMS; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">mapserver-users@lists.osgeo.org</a><br style="font-family: ComicSansMS; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<a href="http://lists.osgeo.org/mailman/listinfo/mapserver-users" style="color: purple; text-decoration: underline; font-family: ComicSansMS; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">http://lists.osgeo.org/mailman/listinfo/mapserver-users</a></div>
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