[Zoo-discuss] Request For Changess: customize styling of output geospatial ComplexDatas

[Rémi Cresson]

Dear all,

I want to propose the following RFC for the zoo-kernel:

Currently in zoo, geospatial images outputs of a WPS process can be 
published as WMS through MapServer, which is very convenient for 
visualization. An extremely useful optional functionality, consisting in 
tagging the complex ProcessOutput whith "msClassify=true" in the .zcfg 
process metadata, enables a classes-oriented styling of the images (i.e. 
random color table). This is achieved in producing a mapfile whith the 
appropriate style.

While this absolutely rocks, I feel that there is still some room for 
improvement of this functionality. In my opinion, I would be really 
interesting to propose more than 2 styling ways (i.e. more than just 
"msClassify=true" or "msClassifiy=false"). Let's not reinvent the wheel 
for image vizualisation and styling: take QGIS for instance, which is 
quite operational on this side. QGIS proposes the essential methods to 
allows the vizualisation of any kind of images. Personally, I use 99% of 
my time the following ones:

1. linear histogram stretching between /min/ and /max/ values of the 
image (e.g. radiometric indice image visualization)

2. linear histogram stretching between /mean-2*std/ and /mean+2*std/ 
values of the image (e.g. natural colors image visualization)

3. random pseudocolor for monoband images (e.g. classification image 
visualization)

4. custom pseudocolor for monoband images (e.g. thematic image 
visualization)

It would be a great improvement to allow the using of those styles (and 
more?) in the MapServer service, conditioned by the WPS process .zcfg 
metadatas of the desired output image. I propose therefore the following 
changes in metadatas for output images styling in the .zcfg:

-remove msClassify[0..1]: boolean

-add msStyle[0..1]: enum of {linear, random, custom} Description: when 
"msStyle=linear", the image is styled using a histogram stretch (all 
bands independently). When "msStyle=random", the image is styled with a 
random color table (equivalent to the obsolete "msClassify=true"). When 
"msStyle=custom", the image is styled with a custom mapfile.

-add msStyleLinear[0..1]: enum of {minmax, meanstd, ...} Description: 
those enums set the low and high values for the linear histogram stretch.

-add msStyleCustom[0..1]: custom mapfile filename, e.g. "myNiceMapfile.map"

Again, those are just suggestions, and are proposed as a basis for 
discussions with the PSC and the zoo community.

I could implement this RFC in a dedicated feature branch.

I am waiting for your feedback, suggestions, opinions.

Regards,

Rémi


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