Saving bil, bip, bsq, and env as 8 bit signed

[gaopeng]

Saving 8 bit signed int data to bil, bip, bsq, and env do not output 8 bit signed int data, instead convert to 8 bit unsigned int.

[warmerdam]

Gao,

What are you referring to by "and env"? I will try to add support for signed 8bit to the EHDR driver - that's the objective here, right?

[warmerdam]

Actually, on review of existing .hdr files I have I am not clear on how to establish whether the raster pixels are to be interpreted as signed or unsigned. Can you provide a .hdr example of a signed 8bit raster?

[gaopeng]

Frank,

There is no real existing sample. But the latest enhancement with PIXELTYPE should be able to handle signed 8 bit, i.e.

NBITS 8 PIXELTYPE SIGNEDINT

"ENV" is ITT-VIS ENVI format. It also should support 8 bit signed.

[warmerdam]

Implemented SIGNEDBYTE support for EHDR driver in trunk (r17283) and testing (r17284).

still need envi support, and then backport to 1.6-esri.

[warmerdam]

Hmm, I'm not sure what "data type" value would correspond with signed byte in an ENVI file. A search on the new turns up this definition for data type.

data type The type of data representation, where 1=8-bit byte; 2=16-bit signed integer; 3=32-bit signed long integer; 4=32-bit floating point; 5=64-bit double-precision floating point; 6=2x32-bit complex, real-imaginary pair of double precision; 9=2x64-bit double-precision complex, real-imaginary pair of double precision; 12=16-bit unsigned integer; 13=32-bit unsigned long integer; 14=64-bit signed long integer; and 15=64-bit unsigned long integer.

but this does not address signedness of the byte type.

[warmerdam]

EHDR changes backported into 1.6-esri branch (r17285).

I don't have a plan to address this for ENVI format at this time.

[gaopeng]

It turned out ENVI format doesn't support 8-bit signed integer type. See below.

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Gao -

No, ENVI (or IDL) doesn't support signed 8 bit pixel values - just unsigned bytes.

-Kirk

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From: Peng Gao pgao@… Sent: Monday, June 22, 2009 2:10 PM To: Kirk Benell Subject: Does ENVI support 8-bit signed integer pixel value? (FW: [GDAL]#2717: Saving bil, bip, bsq, and env as 8 bit signed)

Kirk,

Does ENVI support 8-bit signed integer pixel value?

[gaopeng]

The current document seems to imply the 8 bit signed is supported, ​http://www.gdal.org/frmt_various.html#ENVI.

"GDAL should support reading bil, bip and bsq interleaved formats, and most pixel types are supported, including 8, 16 and 32bit signed and unsigned integers, 32bit and 64 bit floating point, and 32bit and 64bit complex floating point."

[warmerdam]

I have adjusted the docs a bit in r17286. Closing ticket as all work seemed to be done.