| Working with color, cursor, and png to extract information [message #58526] |
Mon, 04 February 2008 11:59  |
Brian Larsen
Messages: 270
Registered: June 2006
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Senior Member |
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OK,
So I am no exactly sure how to ask this question but here goes. As
such I am open for reinterpretation or another solution all
together...
What I want to do:
- Start with a png image from old research (like
http://www.dfanning.com/programs/docs/read_toms_aerosol.jpg)
- read in the png (yes I know the example is a jpg, but it should be
the same procedure)
- extract the "value" at each pixel in the image based on the colorbar
This seems like it should in principle do doable...
Here is what I tried for this attempt:
- read in the image
IDL> image=selectimage(palette=palette)
IDL> help, image, palette
IMAGE BYTE = Array[3, 672, 708]
PALETTE BYTE = Array[256, 3]
- display it
IDL> window, /free, xs=672, ys=708
IDL> tv, image, /true
- select out the part that is the data with cursor and save it
separately
IDL> cursor, x1, y1, /dev ; clicked lower left
IDL> cursor, x2, y2, /dev ; clicked upper right
IDL> image2=image[*,x1:x2, y1:y2]
IDL> window, /free, xs=x2-x1, ys=y2-y1
IDL> tv, image2, /true
- set the x-y vectors using cursor and inspection, and scale_vector
(easy)
now I am stuck, I thought I could set the colortable with
IDL> tvlct, palette
but this seems to still be gray scale (according to cindex)
then I thought I could just pull out the value at each pixel from the
color table then map that back to the values in the colorbar. But I
dont know how, anyone else done something like this?
Normally I extract line plots with g3data (http://www.frantz.fi/
software/g3data.php) but it only does lineplots and not color plots.
Ideas? Comments?
thanks much,
Brian
------------------------------------------------------------ -------------
Brian Larsen
Boston University
Center for Space Physics
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