16 bits & RLE

Hi All,

I made a 16 Bits per channel image file. When I save this file, the file is uncompressed.
When I convert this same file, in 8 bits and save it, photoshop save the file with RLE Compression. (without changing anything between the two saves).

Is there a way to save a 16 bits file with RLE compression, or is it not possible ??

I use Photoshop CS.

Thanks,

Alexandre.

I don't think the RLE format supports 16 bits per channel :-(

Waldo

"Alexandre NEGRI" wrote in message

Hi All,

I made a 16 Bits per channel image file. When I save this file, the file is uncompressed.
When I convert this same file, in 8 bits and save it, photoshop save the file with RLE Compression. (without changing anything between the two saves).

Is there a way to save a 16 bits file with RLE compression, or is it not possible ??

I use Photoshop CS.

Thanks,

Alexandre.

made a 16 Bits per channel image file. When I save this file, the file is uncompressed.
When I convert this same file, in 8 bits and save it, photoshop save the file with RLE Compression. (without changing anything between the two saves).

Correct.

Run Length Encoding is an extremely primitive compression technique that relies on consecutive identical values in order to achieve compression.

16-bit scanned images typically contain noise in the lowest-order bits; a flat expanse of what looks like a solid color typically is not, and will vary by a bit or two in a 16-bit image.

Because RLE compression relies on runs of consecutive identical data, the trivial and unnoticeable variations in 16-bit images prevent RLE from achieving any image compression. RLE-compressed 16-bit images are typically not any smaller than, and may be larger than, uncompressed 16-bit images.

If you need compression, save the image as a TIFF with LZW compression. Be aware, though, that any lossless compression won't work as well on a 16-bit image as on an 8-bit image, for the reasons outlined above.

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In article <3ffc124e$0$7143$>,
Alexandre NEGRI writes:

I made a 16 Bits per channel image file. When I save this file, the file is uncompressed.
When I convert this same file, in 8 bits and save it, photoshop save the file with RLE Compression. (without changing anything between the two saves).

Is there a way to save a 16 bits file with RLE compression, or is it not possible ??

I use Photoshop CS.

You don't say what file format you are using or what kind of images you have.

RLE is almost always useless for 16-bit photos, because the run lengths are mostly 1. RLE would only be useful for something like a studio shot with a solid black background. Even then, the background is unlikely to be a true solid black straight from the camera or scanner. 8-bit photos are much more likely to have long runs than 16-bit photos.

I find that ZIP compression sometimes works well with 16-bit photos, but other times it gives hardly any compression.
--

Warren S. Sarle SAS Institute Inc. The opinions expressed here SAS Campus Drive are mine and not necessarily
(919) 677-8000 Cary, NC 27513, USA those of SAS Institute.

In article <3ffc124e$0$7143$>, Alexandre NEGRI
wrote:

Hi All,

I made a 16 Bits per channel image file. When I save this file, the file is uncompressed.
When I convert this same file, in 8 bits and save it, photoshop save the file with RLE Compression. (without changing anything between the two saves).

Is there a way to save a 16 bits file with RLE compression, or is it not possible ??

No, it is not possible.
RLE compression doesn't work well on 16 bit images (it usually makes them bigger).

Chris