<div dir="ltr"><div><div><div>Hi<br></div>You can transform your image with the following command line:<br><br>gdalwarp -s_srs "+ellps=WGS84 +proj=eqd" -t_srs "+ellps=WGS84 +proj=eck1" in.tif out.tif<br><br></div>The input image must be georeferenced in the equidistant cylindrical projection, with units in meters. See page <a href="http://www.gdal.org/gdalwarp.html">http://www.gdal.org/gdalwarp.html</a>. Other important options are -r, -te and -tr. <br></div>Regards<br><div><div>José Gonçalves<br></div><div><br></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">2016-05-24 23:16 GMT+01:00 Wang Leslie <span dir="ltr"><<a href="mailto:wqyuwss@hotmail.com" target="_blank">wqyuwss@hotmail.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi Norman, Dann,<br>
<br>
Thanks for quick reply. It would be highly appreciated for one sample command on these tools to achieve my goal.<br>
<br>
Best Regards<br>
Leslie<br>
<br>
________________________________________<br>
From: <a href="mailto:proj-bounces@lists.maptools.org">proj-bounces@lists.maptools.org</a> <<a href="mailto:proj-bounces@lists.maptools.org">proj-bounces@lists.maptools.org</a>> on behalf of Norman Vine <<a href="mailto:nhv@cape.com">nhv@cape.com</a>><br>
Sent: Tuesday, May 24, 2016 7:20 AM<br>
To: PROJ.4 and general Projections Discussions<br>
Subject: Re: [Proj] convert from Equidistant Cylindrical to Eckert I<br>
<div class="HOEnZb"><div class="h5"><br>
Hello Leslie<br>
<br>
I suggest using <a href="http://www.gdal.org/gdalwarp.html" rel="noreferrer" target="_blank">http://www.gdal.org/gdalwarp.html</a> todo this<br>
<br>
To avoid the speckling that Daan mentions you want to loop over the new image<br>
pixels and do the inverse projection to find the pixel value in the original image<br>
<br>
gdalwarp takes care of this for you and is built on top of the proj library<br>
<br>
Norman<br>
<br>
> On May 24, 2016, at 3:05 AM, <a href="mailto:strebe@aol.com">strebe@aol.com</a> wrote:<br>
><br>
> Hello Leslie.<br>
><br>
> Your procedure will work. The results will be heavily aliased, which will look like speckling. Some values of (x₁, y₁) will be empty unless the destination map is considerably smaller than the source image.<br>
><br>
> Regards,<br>
> — daan Strebe<br>
><br>
><br>
><br>
> -----Original Message-----<br>
> From: Wang Leslie <<a href="mailto:wqyuwss@hotmail.com">wqyuwss@hotmail.com</a>><br>
> To: proj <<a href="mailto:proj@lists.maptools.org">proj@lists.maptools.org</a>><br>
> Sent: Mon, May 23, 2016 7:37 am<br>
> Subject: [Proj] convert from Equidistant Cylindrical to Eckert I<br>
><br>
> Dear all,<br>
><br>
> I'm new to this tool, and hope to get some advise here.<br>
><br>
> I'm thinking to use your tool to convert a map picture which is based on Equidistant Cylindrical, to another picture based on Eckert I. Since both of them are 2 dimension only (x,y), what I'm gonna to do is:<br>
> - Use proj command to calculate the new mapped coordinate (x1, y1)<br>
> - Set new pixel value at (x1, y1) using original pixel value (x,y)<br>
> - loop for all pixel at original Equidistant Cylindrical picture<br>
><br>
> So can you please help me confirm if one idea can work or not? If yes, what should command line look like? Thanks.<br>
><br>
> Best Regards<br>
> Leslie Qi Wang<br>
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