<html>
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<div class="moz-cite-prefix">Hi Nick,<br>
in fact I don't think there is a bug in the calculator. It is
rather the legend confusing you. I agree that while calculating
there might be some bias with floating number conversation - it
got me either. Otherwise when I use this approach:<br>
<br>
<meta name="qrichtext" content="1">
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;"><!--StartFragment-->"m@1"
< 238 AND "m@1" > 210 AND "m@2" < 123 AND "m@2" > 94
AND "m@3" < 130 AND "m@3" > 98<br>
</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br>
I get a perfectly fitting 0/1 raster. Only that the automated
legend settings do not fit. When setting the
layer-Style-properties to "pseudocolor", color interpretation to
"exact" and then add a class with value "1" then it shows
correct.<br>
</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br>
Just don't use greyscale. Maybe the settings for Greyscale can
be tweeked. Whatsoever, I haven't used that by now. Maybe
someone else has an explanation for this behaviour. Or maybe can
explain how to set the parameters.<br>
</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br>
cheers<br>
</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br>
Stefan<br>
<!--EndFragment--></p>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<style type="text/css">
p, li { white-space: pre-wrap; }
</style><br>
<br>
Am 31.07.2015 um 17:31 schrieb Nick Papadonis:<br>
</div>
<blockquote
cite="mid:201C1A2B-E2C7-449A-ACE2-F9553F256272@gmail.com"
type="cite">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
Hi Stefan,
<div class=""><br class="">
<div>
<blockquote type="cite" class="">
<div class="">On Jul 31, 2015, at 9:37 AM, Stefan Kiefer
<<a moz-do-not-send="true"
href="mailto:st_kiefer@web.de" class="">st_kiefer@web.de</a>>
wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<meta content="text/html; charset=utf-8"
http-equiv="Content-Type" class="">
<div bgcolor="#FFFFFF" text="#000000" class=""> Hi Nick,<br
class="">
back to office I was eager to try by myself. Actually it
seems that the result of multiple AND or multiple layers
- I didn't check this by now - results in values
slightly lower 1 (e.g. 0.9995 in my case). And therefore
maybe rounded to "0". What I have done is the folowing:<br
class="">
<br class="">
</div>
</div>
</blockquote>
<div><br class="">
</div>
<div>
<div>Thanks! I did try your suggestion and it provided me
the results I was seeking of only showing the red routes:</div>
<div><br class="">
</div>
<div>(1/("map@1" < 238 AND "map@1" > 210)) +
(1/("map@2" < 123 AND "map@2" > 94)) + (1/("map@3"
< 130 AND "map@3" > 98))</div>
<div><br class="">
</div>
<div>Perhaps my math is fuzzy. Why would the divisor
resolve this situation whereas multiplier in following has
problems?</div>
<div><br class="">
</div>
<div>((“m@1" < 238 AND “m@1" > 210) * 1) * ((“m@2"
< 123 AND “m@2" > 94) * 1) * ((“m@3" < 130 AND
“m@3" > 98) * 1)</div>
<div><br class="">
</div>
</div>
The floating point values is a why I believe we have a
rounding bug in Raster Calculator. I suspect that during the
calculation a number is converted to floating point, between 0
and 1 (eg 0.9995), and that causes the equation to result in
all 0s. Its unusual that the calculator is performing
floating point math because these are all integer values being
operated on by value comparison operators and other integer
numbers without any division which would cause floating point
conversion or multiplication by a floating point. The numbers
are all whole integers. I was hoping the original author
could chime in on the tool and perhaps this is a bug.</div>
<div><br class="">
</div>
<div>I’m on Mac OSX using 2.10.1 release and see same results on
2.8 release.</div>
<div><br class="">
</div>
<div>I’m suspecting this may be a bug related to:</div>
<div><br class="">
</div>
<div>Raster calculator always returns float32 tiffs</div>
<div><a moz-do-not-send="true"
href="https://hub.qgis.org/issues/10965" class="">https://hub.qgis.org/issues/10965</a></div>
<div>Raster calculator produces only 0 values with conditional
expression</div>
<div><a moz-do-not-send="true"
href="https://hub.qgis.org/issues/11682" class="">https://hub.qgis.org/issues/11682</a></div>
<div><br class="">
</div>
<div>There is this suggestion on the mailing list of how to
resolve, however am a bit confused on the methods. The
workaround may be to reproject the raster layer and I’m unsure
why that’s required:</div>
<div><a moz-do-not-send="true"
href="http://lists.osgeo.org/pipermail/qgis-user/2014-November/029873.html"
class="">http://lists.osgeo.org/pipermail/qgis-user/2014-November/029873.html</a></div>
<div><a moz-do-not-send="true"
href="http://lists.osgeo.org/pipermail/qgis-user/2014-November/029878.html"
class="">http://lists.osgeo.org/pipermail/qgis-user/2014-November/029878.html</a></div>
<div><br class="">
</div>
<div>Thanks again,</div>
<div>Nick</div>
<div><br class="">
<blockquote type="cite" class="">
<div class="">
<div bgcolor="#FFFFFF" text="#000000" class="">
<meta name="qrichtext" content="1" class="">
<div style="margin: 0px; text-indent: 0px;" class=""><!--StartFragment-->(1/("pm2-5-europe-2001-2010@1">240
AND
"pm2-5-europe-2001-2010@1"<250))*(1/("pm2-5-europe-2001-2010@2">139
AND "pm2-5-europe-2001-2010@2"<145)) *
(1/("pm2-5-europe-2001-2010@3">80 AND
"pm2-5-europe-2001-2010@3"<85))<br class="">
<br class="">
</div>
<div style="margin: 0px; text-indent: 0px;" class="">which
results in a perfektly fitting mask of my pseudo
demand.<br class="">
</div>
<div style="margin: 0px; text-indent: 0px;" class="">Mayby
you could verfy this with your data<br class="">
</div>
<div style="margin: 0px; text-indent: 0px;" class=""><br
class="">
cheers<br class="">
<!--EndFragment--></div>
<meta http-equiv="Content-Type" content="text/html;
charset=utf-8" class="">
<style type="text/css" class="">
p, li { white-space: pre-wrap; }
</style><br class="">
Stefan<br class="">
<br class="">
<div class="moz-cite-prefix">Am 31.07.2015 um 08:48
schrieb Stefan Kiefer:<br class="">
</div>
<blockquote
cite="mid:1309030743.598358.1438325334696.JavaMail.open-xchange@omgreatgod.store"
type="cite" class="">
<meta http-equiv="Content-Type" content="text/html;
charset=utf-8" class="">
<div class="">
<div class="">Hi Nick,</div>
<div class="">you are absolutely right. My thought
was, that you get A layer with distinct values to
identify the road. For a mask you are on the right
way, and I either don't understand the behaviour
except that you operate over three layers, which
of course should work.</div>
<div class="">Have you tryed to generate a composit
of the three layers and mask the single values
resulting for road structures? (it's more or less
what I expected from my first approach.)</div>
<div class=""> </div>
<div class="">cheers</div>
<div class=""> </div>
<div class="">Stefan</div>
<br class="">
> Nick Papadonis <a moz-do-not-send="true"
class="moz-txt-link-rfc2396E"
href="mailto:npapadonis@gmail.com"><npapadonis@gmail.com></a>
hat am 31. Juli 2015 um 08:31 geschrieben:<br
class="">
> <br class="">
> <br class="">
> Hi Stefan,<br class="">
> <br class="">
> It’s my understanding black has a value of 0 in
the resulting layer.<br class="">
> <br class="">
> I tried this and it results in similar image to
step (a) and also includes other colors at lower
intensities mixed in with the red. The red has the
highest intensity in the greyscale. I’m looking to
create a binary image with just the colors of red in
the palette I choose and using this trace vectors
over the paths.<br class="">
> <br class="">
> Thanks,<br class="">
> Nick<br class="">
> <br class="">
> > On Jul 31, 2015, at 2:04 AM, Stefan Kiefer
<a moz-do-not-send="true"
class="moz-txt-link-rfc2396E"
href="mailto:st_kiefer@web.de"><st_kiefer@web.de></a>
wrote:<br class="">
> > <br class="">
> > Hi Nick,<br class="">
> > I believe it is black bcause you always
get a value of "1". Unfortunately I can not verify
this, because I have no QGis by this moment. Most
propably you wanted to calculate:<br class="">
> > <br class="">
> > (“m@1" < 238 AND “m@1" > 213 AND
“m@2" < 123 AND “m@2" > 98 AND “m@3" < 125
AND “m@3” > 99) * ((“m@1" < 238 AND “m@1" >
210) * "m@1") + ((“m@2" < 123 AND “m@2" > 94)
* “m@2") + ((“m@3" < 130 AND “m@3" > 98)
*“m@3"))<br class="">
> > <br class="">
> > cheers<br class="">
> > <br class="">
> > Stefan<br class="">
> > <br class="">
> > > Nick Papadonis <a
moz-do-not-send="true"
class="moz-txt-link-rfc2396E"
href="mailto:npapadonis@gmail.com"><npapadonis@gmail.com></a>
hat am 31. Juli 2015 um 07:49 geschrieben:<br
class="">
> > > <br class="">
> > > <br class="">
> > > One more comment. The resulting layer
histogram is showing the pixel range spread over
frequency in floating point values. Is the raster
calculator performing floating point math with
potential rounding error?<br class="">
> > > <br class="">
> > > I found it also interesting that the
following expression resulted in a layer, which when
inspected for band values, has integer values of 2
and 3. 3 being the value I want for the red route.<br
class="">
> > > <br class="">
> > > a) ((“m@1" < 238 AND “m@1" >
210) * 1) + ((“m@2" < 123 AND “m@2" > 94) * 1)
+ ((“m@3" < 130 AND “m@3" > 98) * 1) <br
class="">
> > > <br class="">
> > > I then change the expression to only
use values 2 and greater and this shows properly:<br
class="">
> > > b) ((“m@1" < 238 AND “m@1" >
210) * 1) + ((“m@2" < 123 AND “m@2" > 94) * 1)
+ ((“m@3" < 130 AND “m@3" > 98) * 1) > 2<br
class="">
> > > <br class="">
> > > I then changed the expression to
ensure all three values are obtained and it results
in a black image of 0’s. I was expecting only the
red route to appear as it resulted in value of 3 in
step (a). <br class="">
> > > <br class="">
> > > ((“m@1" < 238 AND “m@1" > 210)
* 1) + ((“m@2" < 123 AND “m@2" > 94) * 1) +
((“m@3" < 130 AND “m@3" > 98) * 1) > 2.1<br
class="">
> > > ((“m@1" < 238 AND “m@1" > 210)
* 1) + ((“m@2" < 123 AND “m@2" > 94) * 1) +
((“m@3" < 130 AND “m@3" > 98) * 1) >= 3<br
class="">
> > > <br class="">
> > > I’m wondering how much testing the
Raster Calculator has gone through and if there is a
possible bug here. Perhaps something to do with
floating point?<br class="">
> > > <br class="">
> > > Thanks again<br class="">
> > > <br class="">
> > > > On Jul 31, 2015, at 12:39 AM,
Nick Papadonis <a moz-do-not-send="true"
class="moz-txt-link-rfc2396E"
href="mailto:npapadonis@gmail.com"><npapadonis@gmail.com></a>
wrote:<br class="">
> > > > <br class="">
> > > > Folks,<br class="">
> > > > <br class="">
> > > > I’m using QGIS 10.1. The
following expressions result in a black raster of
0’s, when I expected only red pixels to appears in
the binary image indicating routes on a map:<br
class="">
> > > > <br class="">
> > > > a) (“m@1" < 238 AND “m@1"
> 213 AND “m@2" < 123 AND “m@2" > 98 AND
“m@3" < 125 AND “m@3” > 99) * 1<br class="">
> > > > b) ((“m@1" < 238 AND “m@1"
> 210) * 1) * ((“m@2" < 123 AND “m@2" > 94)
* 1) * ((“m@3" < 130 AND “m@3" > 98) * 1)<br
class="">
> > > > <br class="">
> > > > I then tried the following
individual expressions for each band as separate
steps (sanity check) and they work to cover the
pixels in range:<br class="">
> > > > c) (“m@1" < 238 AND “m@1"
> 213) * 1<br class="">
> > > > d) (“m@2" < 123 AND “m@2"
> 98) * 1<br class="">
> > > > e) (“m@3" < 125 AND “m@3”
> 99) * 1<br class="">
> > > > <br class="">
> > > > I then tried the following
expression which appears to create a proper
greyscale image focusing on the red pixels. I
replaced the multiplication with addition to see
what was happening:<br class="">
> > > > f) ((“m@1" < 238 AND “m@1"
> 210) * 1) + ((“m@2" < 123 AND “m@2" > 94)
* 1) + ((“m@3" < 130 AND “m@3" > 98) * 1)<br
class="">
> > > > <br class="">
> > > > The resulting raster has a Min =
0 and Max = 1.998. I was expecting it to be Min = 0
and Max = 3. The value of 3 would indicate all 3
bands were positive on color match. I then go to the
layer properties and load calculate min/max again
and it is Min = 0 and Max = 3. I tried to change the
min/max settings on they layer and these settings
will not stay set. The layer goes back to Max =
1.998. What’s even more odd is the max being a
floating point number. I suspect that may be part of
the issue. Anyone know why this is the case for
integer band values? Has anyone successfully used
the Raster Calculator to perform this sort of work
before?<br class="">
> > > > <br class="">
> > > > Thanks again,<br class="">
> > > > Nick<br class="">
> > > <br class="">
> > >
_______________________________________________<br
class="">
> > > Qgis-user mailing list<br class="">
> > > <a moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:Qgis-user@lists.osgeo.org">Qgis-user@lists.osgeo.org</a><br
class="">
> > > <a moz-do-not-send="true"
class="moz-txt-link-freetext"
href="http://lists.osgeo.org/mailman/listinfo/qgis-user">http://lists.osgeo.org/mailman/listinfo/qgis-user</a><br
class="">
> </div>
<br class="">
<fieldset class="mimeAttachmentHeader"></fieldset>
<br class="">
<pre class="" wrap="">_______________________________________________
Qgis-user mailing list
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:Qgis-user@lists.osgeo.org">Qgis-user@lists.osgeo.org</a>
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://lists.osgeo.org/mailman/listinfo/qgis-user">http://lists.osgeo.org/mailman/listinfo/qgis-user</a></pre>
</blockquote>
<br class="">
</div>
_______________________________________________<br
class="">
Qgis-user mailing list<br class="">
<a moz-do-not-send="true"
href="mailto:Qgis-user@lists.osgeo.org" class="">Qgis-user@lists.osgeo.org</a><br
class="">
<a class="moz-txt-link-freetext" href="http://lists.osgeo.org/mailman/listinfo/qgis-user">http://lists.osgeo.org/mailman/listinfo/qgis-user</a></div>
</blockquote>
</div>
<br class="">
</div>
</blockquote>
<br>
</body>
</html>