[Qgis-user] Qgis-user Layer question
Jonathan Webb
jonathan at jwebbgis.co.uk
Thu Jul 30 23:44:41 PDT 2015
I've converted road polylines to polygons before by buffering. You may have to do different road grades/widths in several stages.
On 31 July 2015 05:39:15 BST, qgis-user-request at lists.osgeo.org wrote:
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>------------------------------------------------------------------------
>
>Today's Topics:
>
> 1. Layer question (Shane)
> 2. Re: Layer question (Tom Lennon)
> 3. Re: Layer question (Bernd Vogelgesang)
> 4. Re: Layer question (Nicolas Cadieux)
> 5. Re: How to convert raster routes into vector format?
> (Nick Papadonis)
> 6. Raster Calculator Expression to determine color (Nick Papadonis)
> 7. Re: Raster Calculator Expression to determine color (Nyall Dawson)
> 8. Re: Raster Calculator Expression to determine color
> (Nick Papadonis)
> 9. Re: Raster Calculator Expression to determine color
> (Nick Papadonis)
> 10. Re: Raster Calculator bug? (Nick Papadonis)
>
>
>------------------------------------------------------------------------
>
>From: Shane <shaned173 at gmail.com>
>To: qgis-user at lists.osgeo.org
>Sent: Thu Jul 30 20:05:09 BST 2015
>Subject: [Qgis-user] Layer question
>
> Hi group,
>
> I have a layer with roads which are lines having a style of gray
>with thin black outlines on either side. Another layer (parking lots)
>has polygons having the same color as the roads but not outlined. The
>parking lot layer is above the road layer in rendering order. So road
>outlines are hidden by the parking lot layer when a parking lot
>intersects a road.
>
> Here's the trouble - having parking lots with no outline, but roads
>with outlines looks odd. Is there some way to have the outlines of
>both
>road and parking lot layers removed from rendering when these two
>features cross?
>
> One method I've considered is to draw the roads and parking lots as
>polygons in the same layer? It would make drawing the roads
>non-trivial, but the problem with outlines would be eliminated.
>
> Shane
>
>
>
>
>------------------------------------------------------------------------
>
>From: Tom Lennon <tolennon at gmail.com>
>To: Shane <shaned173 at gmail.com>
>Cc: qgis-user <qgis-user at lists.osgeo.org>
>Sent: Thu Jul 30 22:11:17 BST 2015
>Subject: Re: [Qgis-user] Layer question
>
>Hi Shane:
>Have you tried moving the parking lot layer to below the road layer?
>That way roads over parking lots would always show.
>
>Tom
>
>On Thu, Jul 30, 2015 at 3:05 PM, Shane <shaned173 at gmail.com> wrote:
>
>> Hi group,
>>
>> I have a layer with roads which are lines having a style of gray
>with
>> thin black outlines on either side. Another layer (parking lots) has
>> polygons having the same color as the roads but not outlined. The
>parking
>> lot layer is above the road layer in rendering order. So road
>outlines are
>> hidden by the parking lot layer when a parking lot intersects a road.
>>
>> Here's the trouble - having parking lots with no outline, but
>roads
>> with outlines looks odd. Is there some way to have the outlines of
>both
>> road and parking lot layers removed from rendering when these two
>features
>> cross?
>>
>> One method I've considered is to draw the roads and parking lots
>as
>> polygons in the same layer? It would make drawing the roads
>non-trivial,
>> but the problem with outlines would be eliminated.
>>
>> Shane
>>
>> _______________________________________________
>> Qgis-user mailing list
>> Qgis-user at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/qgis-user
>>
>
>
>
>--
>tolennon at gmail.com
>
>
>------------------------------------------------------------------------
>
>From: Bernd Vogelgesang <bernd.vogelgesang at gmx.de>
>To: qgis-user at lists.osgeo.org
>Sent: Thu Jul 30 22:50:36 BST 2015
>Subject: Re: [Qgis-user] Layer question
>
>Hi Shane,
>I think without a screenshot, we have no chance to really get an idea
>what
>it's all about.
>Best to use a service like http://imgur.com/ and post the link cause
>the
>list will bounce too heavy attachments.
>
>Bernd
>
>
>
>Am 30.07.2015, 23:11 Uhr, schrieb Tom Lennon <tolennon at gmail.com>:
>
>> Hi Shane:
>> Have you tried moving the parking lot layer to below the road layer?
>> That way roads over parking lots would always show.
>>
>> Tom
>>
>> On Thu, Jul 30, 2015 at 3:05 PM, Shane <shaned173 at gmail.com> wrote:
>>> Hi group,
>>>
>>> I have a layer with roads which are lines having a style of gray
>with
>>> thin black outlines on either side. Another layer >>(parking lots)
>has
>>> polygons having the same color as the roads but not outlined. The
>>> parking lot layer is above the road layer in >>rendering order. So
>
>>> road outlines are hidden by the parking lot layer when a parking lot
>
>>> intersects a road.
>>>
>>> Here's the trouble - having parking lots with no outline, but
>roads
>>> with outlines looks odd. Is there some way to have the >>outlines
>of
>>> both road and parking lot layers removed from rendering when these
>two
>>> features cross?
>>>
>>> One method I've considered is to draw the roads and parking lots
>as
>>> polygons in the same layer? It would make drawing the >>roads
>>> non-trivial, but the problem with outlines would be eliminated.
>>>
>>> Shane
>>>
>>> _______________________________________________
>>> Qgis-user mailing list
>>> Qgis-user at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/qgis-user
>>
>>
>>
>> --tolennon at gmail.com
>
>
>
>--
>Bernd Vogelgesang
>Siedlerstraße 2
>91083 Baiersdorf/Igelsdorf
>Tel: 09133-825374
>
>------------------------------------------------------------------------
>
>From: Nicolas Cadieux <nicolas.cadieux at archeotec.ca>
>To: qgis-user at lists.osgeo.org
>Sent: Thu Jul 30 23:07:50 BST 2015
>Subject: Re: [Qgis-user] Layer question
>
>Hi,
>You can play with the layer blending. You can use "multiply" ,
>"add", "subtract"... (something like that, I am not in front of a
>computer). There are also the same blending options in the vector
>object styling so that you can select what happens when two objects
>intersect in the same layer.
>Maybe that could help?
>Nicolas Cadieux M.Sc.
>Les Entreprises Archéotec inc.
>8548, rue Saint-Denis Montréal H2P 2H2
>Téléphone: 514.381.5112 Fax: 514.381.4995
>www.archeotec.ca
>On Jul 30, 2015 5:45 PM, "berndv. [via OSGeo.org]"
><ml-node+s1560n5217887h58 at n6.nabble.com> wrote:
>
>
>
>
>Hi Shane, I think without a screenshot, we have no chance to really get
>an idea what it's all about. Best to use a service like
>http://imgur.com/ and post the link cause the list will bounce too
>heavy attachments. Bernd Am 30.07.2015, 23:11 Uhr, schrieb Tom Lennon
>< [hidden email] >: <blockquote style="border-left:2px
>solid #cccccc;padding:0 1em" style="margin:0 0
>0.8ex;border-left:#0000ff 2px solid;padding-left:1ex"> Hi
>Shane: Have you tried moving the parking lot layer to below the road
>layer? That way roads over parking lots would always show. Tom On Thu,
>Jul 30, 2015 at 3:05 PM, Shane < [hidden email] > wrote:
><blockquote style="border-left:2px solid #cccccc;padding:0
>1em" style="margin:0 0 0 0.8ex;border-left:1px #ccc
>solid;padding-left:1ex"> Hi group,
>
> I have a layer with roads which are lines having a style of gray
>with thin black outlines on either side. Another layer (parking lots)
>has polygons having the same color as the roads but not outlined. The
>parking lot layer is above the road layer in rendering order. So road
>outlines are hidden by the parking lot layer when a parking lot
>intersects a road.
>
> Here's the trouble - having parking lots with no outline, but
>roads with outlines looks odd. Is there some way to have the outlines
>of both road and parking lot layers removed from rendering when these
>two features cross?
>
> One method I've considered is to draw the roads and parking lots
>as polygons in the same layer? It would make drawing the roads
>non-trivial, but the problem with outlines would be eliminated.
>
> Shane
>
>_______________________________________________
>Qgis-user mailing list
>[hidden email]
>http://lists.osgeo.org/mailman/listinfo/qgis-user
>-- [hidden email]
>
>-- Bernd Vogelgesang Siedlerstraße 2 91083 Baiersdorf/Igelsdorf Tel:
>09133-825374 _______________________________________________
>Qgis-user mailing list
>[hidden email]
>http://lists.osgeo.org/mailman/listinfo/qgis-user
>
>
>
>
>
>
>
>
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>View this message in context:
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>
>------------------------------------------------------------------------
>
>From: Nick Papadonis <npapadonis at gmail.com>
>To: "Håvard Tveite" <havard.tveite at nmbu.no>
>Cc: qgis-user at lists.osgeo.org
>Sent: Fri Jul 31 00:45:56 BST 2015
>Subject: Re: [Qgis-user] How to convert raster routes into vector
>format?
>
>Hi Havard,
>
>Unfortunately, the expression below results in a complete black TIFF.
>I am referencing the correct layer. Any ideas?
>
>Thanks
>Nick
>
>> On Jul 29, 2015, at 4:34 PM, Håvard Tveite <havard.tveite at nmbu.no>
>wrote:
>>
>> With QGIS 2.10, the following should work (probably also OK
>> for earlier versions).
>>
>> Check the band values of your colour using the info button,
>> and use the values in the expression below (assuming the
>> name of your raster layer is yourraster) instead of 116, 20
>> and 31:
>>
>> ("yourraster at 1" = 116 AND "yourraster at 2" = 20 AND "yourraster at 3" =
>31) * 1
>>
>> This should give you a binary raster with 1 in the pixels
>> that have your colour and 0 in the pixels with other colours.
>>
>> In the style dialogue you can use the following to see the
>> resulting binary image:
>> Colour gradient: "white to black"
>> Min: 0
>> Max: 1
>>
>> You should be able to use r.thin on that image, but I am not
>> able to test this now, as I am on Ubuntu, and have not been
>> able to get GRASS to work through Processing on that platform
>> for QGIS 2.10.
>>
>> Håvard
>>
>> On 29. juli 2015 16:40, Nick Papadonis wrote:
>>> Hi Håvard,
>>>
>>> I found the raster calculator and read the online manual for it,
>however am still a bit lost. I was also playing with the Style
>properties and color bands last night to try to accomplish this. I was
>unable to get a single binary image with the single color (red in this
>case). I think the understand the r.thin suggestion and that it will
>thin the single color thick lines for vectorization. Appreciate if you
>can expand on obtaining a binary skeleton of the one color of the
>trails.
>>>
>>> Thanks again,
>>> Nick
>>>
>>>> On Jul 29, 2015, at 7:18 AM, Havard Tveite <havard.tveite at nmbu.no>
>wrote:
>>>>
>>>> If you are going to use GRASS r.to.vect (for instance through QGIS
>>>> Processing), you will need a binary skeleton image.
>>>> You could get one by using the raster calculator to extract
>>>> your single colour as a binary image, and then GRASS r.thin
>>>> (available in QGIS Processing) to get the skeleton.
>>>>
>>>> Håvard
>>>>
>>>> On 29/7/2015 8:36:AM, Nick Papadonis wrote:
>>>>> Hi Folks,
>>>>>
>>>>> I have a map with numerous trails in a single color and would like
>to vectorize these. Is there a mode Qgis can be placed in such that a
>color can be selected for inclusion in the vectorization process? I.e.
>to make converting these routes to vector format easier?
>>>>>
>>>>> Thanks again
>>>>> _______________________________________________
>>>>> Qgis-user mailing list
>>>>> Qgis-user at lists.osgeo.org
>>>>> http://lists.osgeo.org/mailman/listinfo/qgis-user
>>>>>
>>>
>
>
>
>
>------------------------------------------------------------------------
>
>From: Nick Papadonis <npapadonis at gmail.com>
>To: Qgis-user at lists.osgeo.org
>Sent: Fri Jul 31 02:07:44 BST 2015
>Subject: [Qgis-user] Raster Calculator Expression to determine color
>
>HI Folks,
>
>I’m trying to use the following expression to pick up the red colored
>routes on a map in which I used the info pointer tool to get the band
>values for the color.
>
>(“m at 1" < 238 AND “m at 1" > 213 AND “m at 2" < 123 AND “m at 2" > 98 AND “m at 3" <
>125 AND “m at 3" < 99) * 1
>
>Unfortunately, when this expression is used the resulting map is black
>with no other pixels for the detected color.
>
>If I break down this expression to a simple “greater than” line for
>single band, then things work.
>
>Does anyone know where this expression needs to be corrected?
>
>Thanks again,
>Nick
>
>
>------------------------------------------------------------------------
>
>From: Nyall Dawson <nyall.dawson at gmail.com>
>To: Nick Papadonis <npapadonis at gmail.com>
>Cc: Qgis-user at lists.osgeo.org
>Sent: Fri Jul 31 02:29:34 BST 2015
>Subject: Re: [Qgis-user] Raster Calculator Expression to determine
>color
>
>On 31 Jul 2015 11:07 am, "Nick Papadonis" <npapadonis at gmail.com> wrote:
>>
>> HI Folks,
>>
>> I’m trying to use the following expression to pick up the red colored
>routes on a map in which I used the info pointer tool to get the band
>values for the color.
>>
>> (“m at 1" < 238 AND “m at 1" > 213 AND “m at 2" < 123 AND “m at 2" > 98 AND “m at 3"
><
>125 AND “m at 3" < 99) * 1
>
>Should that last check be "m at 3" > 99?
>
>Nyall
>
>>
>> Unfortunately, when this expression is used the resulting map is
>black
>with no other pixels for the detected color.
>>
>> If I break down this expression to a simple “greater than” line for
>single band, then things work.
>>
>> Does anyone know where this expression needs to be corrected?
>>
>> Thanks again,
>> Nick
>> _______________________________________________
>> Qgis-user mailing list
>> Qgis-user at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/qgis-user
>
>
>------------------------------------------------------------------------
>
>From: Nick Papadonis <npapadonis at gmail.com>
>To: Nyall Dawson <nyall.dawson at gmail.com>
>Cc: Qgis-user at lists.osgeo.org
>Sent: Fri Jul 31 02:30:44 BST 2015
>Subject: Re: [Qgis-user] Raster Calculator Expression to determine
>color
>
>
>> On Jul 30, 2015, at 9:29 PM, Nyall Dawson <nyall.dawson at gmail.com>
>wrote:
>>
>>
>> On 31 Jul 2015 11:07 am, "Nick Papadonis" <npapadonis at gmail.com
><mailto:npapadonis at gmail.com>> wrote:
>> >
>> > HI Folks,
>> >
>> > I’m trying to use the following expression to pick up the red
>colored routes on a map in which I used the info pointer tool to get
>the band values for the color.
>> >
>> > (“m at 1" < 238 AND “m at 1" > 213 AND “m at 2" < 123 AND “m at 2" > 98 AND
>“m at 3" < 125 AND “m at 3" < 99) * 1
>>
>> Should that last check be "m at 3" > 99?
>>
>>
>Yeah, I changed that and still same results. If I specify on > and
>remove the < expressions, then everything works. Very odd considering
>the color is within the range above (with the line you referenced
>fixed).
>
>Thanks
>> Nyall
>>
>> >
>> > Unfortunately, when this expression is used the resulting map is
>black with no other pixels for the detected color.
>> >
>> > If I break down this expression to a simple “greater than” line for
>single band, then things work.
>> >
>> > Does anyone know where this expression needs to be corrected?
>> >
>> > Thanks again,
>> > Nick
>> > _______________________________________________
>> > Qgis-user mailing list
>> > Qgis-user at lists.osgeo.org <mailto:Qgis-user at lists.osgeo.org>
>> > http://lists.osgeo.org/mailman/listinfo/qgis-user
><http://lists.osgeo.org/mailman/listinfo/qgis-user>
>
>
>------------------------------------------------------------------------
>
>From: Nick Papadonis <npapadonis at gmail.com>
>To: Nyall Dawson <nyall.dawson at gmail.com>, Qgis-user at lists.osgeo.org
>Sent: Fri Jul 31 02:56:24 BST 2015
>Subject: Re: [Qgis-user] Raster Calculator Expression to determine
>color
>
>
>> On Jul 30, 2015, at 9:29 PM, Nyall Dawson <nyall.dawson at gmail.com>
>wrote:
>> On 31 Jul 2015 11:07 am, "Nick Papadonis" <npapadonis at gmail.com
><mailto:npapadonis at gmail.com>> wrote:
>> >
>> > HI Folks,
>> >
>> > I’m trying to use the following expression to pick up the red
>colored routes on a map in which I used the info pointer tool to get
>the band values for the color.
>> >
>> > (“m at 1" < 238 AND “m at 1" > 213 AND “m at 2" < 123 AND “m at 2" > 98 AND
>“m at 3" < 125 AND “m at 3" < 99) * 1
>>
>> Should that last check be "m at 3" > 99?
>>
>>
>
>I corrected above to:
>(“m at 1" < 238 AND “m at 1" > 213 AND “m at 2" < 123 AND “m at 2" > 98 AND “m at 3" <
>125 AND “m at 3” > 99) * 1
>
>with the same results which is black output tiff.
>
>I then tried individual expressions for each band as separate steps
>(sanity check):
>(“m at 1" < 238 AND “m at 1" > 213) * 1
>(“m at 2" < 123 AND “m at 2" > 98) * 1
>(“m at 3" < 125 AND “m at 3” > 99) * 1
>
>These all produce a masked image, however masked incorrectly because
>I’m evaluating only a single band in the Raster Calculator.
>
>When I combine evaluation of bands as above or below to pick pixels in
>color range:
>
>((“m at 1" < 238 AND “m at 1" > 210) AND (“m at 2" < 123 AND “m at 2" > 94) AND
>(“m at 3" < 130 AND “m at 3" > 98)) * 1
>
>I get a black image with no matches. I expected at least one pixel
>identified using this expression because I evaluate a pixel at 224,
>108, 115 and there are many other pixels in above range.
>
>Does anyone know if my expression needs correction or the Raster
>Calculator can only evaluate a single band in the expression?
>
>Thanks again,
>Nick
>
>> Nyall
>>
>> >
>> > Unfortunately, when this expression is used the resulting map is
>black with no other pixels for the detected color.
>> >
>> > If I break down this expression to a simple “greater than” line for
>single band, then things work.
>> >
>> > Does anyone know where this expression needs to be corrected?
>> >
>> > Thanks again,
>> > Nick
>> > _______________________________________________
>> > Qgis-user mailing list
>> > Qgis-user at lists.osgeo.org <mailto:Qgis-user at lists.osgeo.org>
>> > http://lists.osgeo.org/mailman/listinfo/qgis-user
><http://lists.osgeo.org/mailman/listinfo/qgis-user>
>
>
>------------------------------------------------------------------------
>
>From: Nick Papadonis <npapadonis at gmail.com>
>To: Qgis-user at lists.osgeo.org
>Sent: Fri Jul 31 05:39:12 BST 2015
>Subject: Re: [Qgis-user] Raster Calculator bug?
>
>Folks,
>
>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:
>
>a) (“m at 1" < 238 AND “m at 1" > 213 AND “m at 2" < 123 AND “m at 2" > 98 AND
>“m at 3" < 125 AND “m at 3” > 99) * 1
>b) ((“m at 1" < 238 AND “m at 1" > 210) * 1) * ((“m at 2" < 123 AND “m at 2" > 94)
>* 1) * ((“m at 3" < 130 AND “m at 3" > 98) * 1)
>
>I then tried the following individual expressions for each band as
>separate steps (sanity check) and they work to cover the pixels in
>range:
>c) (“m at 1" < 238 AND “m at 1" > 213) * 1
>d) (“m at 2" < 123 AND “m at 2" > 98) * 1
>e) (“m at 3" < 125 AND “m at 3” > 99) * 1
>
>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:
>f) ((“m at 1" < 238 AND “m at 1" > 210) * 1) + ((“m at 2" < 123 AND “m at 2" > 94)
>* 1) + ((“m at 3" < 130 AND “m at 3" > 98) * 1)
>
>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?
>
>Thanks again,
>Nick
>
>
>------------------------------------------------------------------------
>
>_______________________________________________
>Qgis-user mailing list
>Qgis-user at lists.osgeo.org
>http://lists.osgeo.org/mailman/listinfo/qgis-user
--
Jonathan Webb
Freelance GIS specialist
07941 921905
www.jwebbgis.co.uk
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