[Openexr-devel] Re: Unable to write single black pixel image

[Florian Kainz]

Charles Henrich wrote:
> 
> In version 1.0.7 under linux if you try and write a single black pixel with
> either zlib compression methods, you the library will fail with:
> 
> Failed to write pixel data to image file "/tmp/test.exr". Data compression
> (zlib) failed.
> 
> Is this a known issue with 1.0.7?
> 
> -Crh
> 

For very small images, class ZipCompressor in version 1.0.7
sometimes allocates a buffer for the compressed pixels that
is too small, and zlib compression fails.  This has been fixed 
in version 1.1.0. (I tried writing a single black pixel with
ZIP and ZIPS compression, and it worked.)

You can patch file ImfZipCompressor.cpp if you don't want to 
switch to OpenEXR 1.1.0.  Change line 62,

    _outBuffer = new char [maxScanLineSize * numScanLines * 3 / 2];

to

    _outBuffer = new char [maxScanLineSize * numScanLines * 3 / 2 + 100];

and line 141,

    uLongf outSize = inSize * 3 / 2;

to

    uLongf outSize = inSize * 3 / 2 + 100;