hey Gang,
Gary at Apache-Commons-Imaging has some questions regarding a monoband TIF i
provided. would one of you with a deeper knowledge of rasters (Peppe, Jukka,
both?) answer him please in the ticket linked below (you need an account, so
may have to register, but it's painless and fast).
thanks.. ede
-------- Forwarded Message --------
Subject: [jira] [Commented] (IMAGING-267) Colorful rendering of b/w Monoband TIF
Date: Tue, 22 Sep 2020 00:06:00 +0000 (UTC)
From: Gary Lucas (Jira) <j...@apache.org>
To: edgar.sol...@web.de
[
https://issues.apache.org/jira/browse/IMAGING-267?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17199709#comment-17199709
]
Gary Lucas commented on IMAGING-267:
------------------------------------
Thank you for posting the images. They may help to answer some issues I've
wondered about for awhile. I've inspected their content and I have a few
questions for you.
First off, this TIFF appears to be geophysical data. But there are no GeoTIFF
tags bundled with the image. Judging from the ModelTiepointTag, it appears that
the original image was configured using a projected coordinate system, maybe a
UTM zone. It might help me understand this better if there were more location
information attached to the image. Do you have that information?
Secondly, I note that this TIFF file is not strictly-speaking an image , but is
actually numerical data stored using the TIFF standard floating-point raster
format. My guess is that it's probably elevations. The ability to process TIFF
files containing floating point data was introduced in the most recent release
of Commons Imaging.
One challenge of floating point images is how to map the range of values to
gray scale. In this case, the following text gives the TIFF Tags attached to
the image:
Directory 0 Has TIFF Image Data, description: Root
256 (0x100: ImageWidth): 601 (1 Long)
257 (0x101: ImageLength): 410 (1 Long)
258 (0x102: BitsPerSample): 32 (1 Short)
259 (0x103: Compression): 1 (1 Short)
262 (0x106: PhotometricInterpretation): 1 (Indicates "zero is black")
277 (0x115: SamplesPerPixel): 1 (1 Short)
278 (0x116: RowsPerStrip): 8 (1 Long)
339 (0x153: SampleFormat): 3 (Indicates float-point format)
33550 (0x830e: ModelPixelScaleTag): 25.0, 25.0 (2 Double)
33922 (0x8482: ModelTiepointTag): 0.0, 0.0, 0.0, 262846.525725, 4464275.0, 0.0
(6 Double)
42113 (0xa481: GDALNoData): 45, 51, 50, 55, 54, 56, 46, 48 (8 Byte)
Upon inspection, I find that the values in the image range from 514 to 2410.
Commons Imaging does have an API element called the
custom-photometric-interpreter that lets an application specify how colors (or
gray tones) are assigned to elevations. So in this case, I was able to render
the data by specifying the following lines:
{{ HashMap<String, Object> params = new HashMap<>(); }}
{{ PhotometricInterpreterFloat pi = }}
{{ new PhotometricInterpreterFloat(514.0f, 2410.0f);}}
{{ params.put(TiffConstants.PARAM_KEY_CUSTOM_PHOTOMETRIC_INTERPRETER, pi);}}
{{ BufferedImage bImage = Imaging.getBufferedImage(target, params);}}
{{ ImageIO.write(bImage, "JPG", output);}}
I've attached the image I produced (ISSUE_267.JPG). However, to create it, I
had to know before hand what the range of values was. So my application does a
few extra steps that I did not show in the example above. I was wondering how
the software you used handles this issue. Is it all automatic?
Also, a second question I had is that the PhotometricInterpretation tag given with your
image is 1, which means "0 is black". In other words, the palette should
range from the darkest shading for the lowest numerical values to the lightest shading
for the highest values. However, in looking at your image I notice that the lowest value
pixels are drawn in the lightest colors, which seems to contradict the setting in the
source TIFF file. In the image I've attached, the lowest value pixels are draw in the
darkest colors, which is consistent with the specification in the TIFF image. Is there
some setting in the application you used that overwrites the settings from the TIFF file?
!ISSUE_267.JPG!
Colorful rendering of b/w Monoband TIF
--------------------------------------
Key: IMAGING-267
URL: https://issues.apache.org/jira/browse/IMAGING-267
Project: Commons Imaging
Issue Type: Bug
Reporter: edgar soldin
Priority: Major
Attachments: ISSUE_267.JPG, mdt25a-commons.png, mdt25a-sextante.png,
mdt25a.tif
see attached images.
mdt25a.tif - the original tif
mdt25a-commons.png - as rendered/read with Commons Imaging
mdt25a-sextante.png - as rendered /read properly with ImageIO-Core from
https://github.com/jai-imageio/jai-imageio-core
thanks!.. ede
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