| Re: Significant Update of cgImage [message #78629 is a reply to message #78628] |
Mon, 05 December 2011 00:46   |
Fabzou
Messages: 76
Registered: November 2010
|
Member |
|
|
Ah, and it seems to me that cgContour is broken in the last update:
IDL> data = cgDemoData(18)
IDL> cgContour, data, COLOR='grey'
Traceback Report from CGCOLOR:
% Expression must be a scalar or 1 element array in this context:
<BYTE Array[6]>.
% Execution halted at: CGCOLOR 589
/home/fab/disk/IDLWorkspace/COYOTE/cgcolor.pro
% CGCONTOUR 724
/home/fab/disk/IDLWorkspace/COYOTE/cgcontour.pro
% $MAIN$
On 12/05/2011 09:36 AM, Fabzou wrote:
> Hi David,
>
> Nice updates. I think that most of the features (scaling, missing) have
> been allready implemented upstream by people (like me!) who needed this
> for long, but I may change some of my code
>
> The same applies for the automatic window XY ratio. In my case the most
> interesting feature would be do be able to produce a display
> automatically that takes in account the XY ratio of the "image + color
> bar + colorbar tags" which are almost allways present when you display
> any kind of data.
>
> Thanks a lot,
>
> Fab
>
>
>
> On 12/04/2011 06:58 PM, David Fanning wrote:
>> Folks,
>>
>> I wanted to alert you to a couple of significant feature
>> updates to cgImage.
>>
>> As I work on my map projection book, I have been using
>> a lot of GeoTiff images. These images are easy to
>> navigate and georegister, and I have developed software
>> that can read a GeoTiff file and display the image with
>> map annotations, etc. All of that works nicely.
>>
>> The problem is that many of these Tiff images are low
>> contrast, have missing data values in them, etc. This
>> is the problem that is addressed in this update of
>> cgImage.
>>
>> I have modified cgImage so that if you are displaying
>> a 2D image array (this does NOT apply to 24-bit color
>> images!) you now have the ability to scale or stretch
>> these images eight different ways. Basically, you now
>> have the stretching capability of XStretch directly
>> in cgImage. What this means is that not only can you
>> do a straight linear scaling of the data before display
>> (the purpose of the old SCALE keyword), but you can
>> also do Log, Gamma, and Gaussian scaling, do
>> histogram clipping in various ways, etc.
>>
>> For example, many of these images look best when a
>> two percent histogram clipping is used (e.g. ClipScl).
>> This is the same default clipping that ENVI uses.
>> You can affect such a clip like this:
>>
>> IDL> cgImage, image2d, Stretch="CLIP"
>>
>> Possible values for the STRETCH keyword are: LINEAR,
>> CLIP, GAMMA, LOG, ASINH, SQUAREROOT, EQUALIZATION,
>> GAUSSIAN, and MODIS. Alternatively, you can use index
>> numbers in place of these names. In other words, the
>> command above can also be written like this:
>>
>> IDL> cgImage, image2d, Stretch=2
>>
>> The old SCALE keyword simple chooses a LINEAR stretch.
>> Additional keywords are added that will set the parameters
>> for the different stretches available.
>>
>> Another problem with many GeoTiff images is that they
>> have missing data in them. So cgImage has also been modified
>> with three additional keywords to allow you to handle this
>> missing data appropriately. These keywords are:
>>
>> Missing_Value - Used to specify the missing data value in the image.
>> Missing_Index - Specify the missing index in the output image.
>> Missing_Color - Specify color of the missing data in output image.
>>
>> Suppose, for example, missing data is indicated by the value
>> -32767 and you would like to display this missing data in a
>> white color using color index 255 (the default missing color
>> index). Then you could set up and display your image like this:
>>
>> IDL> cgLoadct, 33, NColors=254
>> IDL> cgImage, image2d, Missing_Value=-32767, Missing_Color='white', $
>> Stretch="LINEAR"
>>
>> The missing data values are now set to !Values.F_NAN before the
>> scaling is done. The scaling is done into the values 0 to 254.
>> Then the missing data indices are set equal to 255, the
>> missing value index. The resulting image shows the missing
>> values in the color you specify.
>>
>> I want to mention one other change. I often want to display
>> these images in graphics windows having the same aspect ratio
>> as the image itself. A new DISPLAY keyword to cgImage will
>> create such a graphics window for me and display the image in
>> that graphics window. If the DISPLAY keyword is used with
>> the WINDOW keyword, and new cgWindow will be created. Otherwise
>> the graphics window will be created with cgDisplay.
>>
>> IDL> cgImage, image2d, Missing_Value=-32767, Missing_Color='white', $
>> Stretch="LINEAR", /Display, /Window
>>
>> If a cgWindow is opened in this way, the aspect ratio of the
>> window is confined to the aspect ratio of the image as the
>> window is resized.
>>
>> A number of other routines were slightly modified to work
>> smoothly with new functionality in cgImage. This would
>> be a good time to update your Coyote Library:
>>
>> http://www.idlcoyote.com/programs/zip_files/coyoteprograms.z ip
>>
>> You can read about the new keywords in the updated cgImage
>> documentation:
>>
>> http://www.idlcoyote.com/idldoc/cg/cgimage.html
>>
>> Cheers,
>>
>> David
>>
>
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
