commons-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Gary Lucas (JIRA)" <>
Subject [jira] [Updated] (IMAGING-102) TIFF parser does not support floating-point images
Date Tue, 19 Feb 2013 12:41:12 GMT


Gary Lucas updated IMAGING-102:

    Attachment: Sample64BitFloatingPointPix451x337.tif

Sample Image from AvMet Applicatons, Inc. Used with permission.
> TIFF parser does not support floating-point images
> --------------------------------------------------
>                 Key: IMAGING-102
>                 URL:
>             Project: Commons Imaging
>          Issue Type: Bug
>            Reporter: Gary Lucas
>         Attachments: Sample64BitFloatingPointPix451x337.tif
> The TIFF specification defines a data form for storing pixels as either 32-bit or 64-bit
floating point values given in the IEEE 754 format. The TIFF-6 specification is actually incomplete
in this regard, but typically such values are stored as data in the range [0,1] with 9999
(or other values out of the range zero to one) used to indicate "no-data".   Typically, values
are rendered in gray tones. The TIFF "SampleFormat" tag indicates when data is encoded in
this form.
> Commons Imaging does not currently support data that uses the floating-point sample format.
 It does define a constant in the file which is named SAMPLE_FORMAT_VALUE_IEEE_FLOATING_POINT.
 But this constant is not used in the code.
> I propose to at least implement read-support for images in this format. I am working
to obtain permission to post a sample image which I will attach to this tracker item in the
> Currently, the TIFF parser provides output in the form of a BufferedImage. For the initial
implementation, I recommend staying with that convention and resolving the floating point
values to gray tones. Although this approach has the disadvantage that it will not provide
an API for extracting the original floating-point values, it seems to me the safest tactic
for an initial implementation.
> Development will require some caution to avoid degrading parser performance. The BitImageStream.readBits()
method which reads samples (pixels) from the source data, currently returns the Java int type,
which only supports 32 bits.  To support 64 bits, this function would have to return a Java
long.  The development effort will require testing to ensure that making a change of this
type does not degrade performance for the mainstream TIFF data formats (probably this is only
an issue on 32-bit operating systems).
> For those of you who are asking why someone would choose to store data using floating-point
values (at the cost of 64 bits per pixel)... I don't really know. Putting aside the fact that
it's in the spec (sort of) and somebody wants me to plot data from such images, I would have
to say the motivation would probably be using TIFF files as a way of storing arbitrary data
in gridded fields.  The proposed changes wouldn't satisfy their requirements, but it is a
first step in that direction.

This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see:

View raw message