#179 Saving HDR files a mess

Luminance HDR 2.4.0

Saving HDR files is poorly implemented and ambiguous.

The first issue is the "HDR Options" tab in Preferences, which lets you choose either "LogLuv TIFF" or "Float TIFF". This is poorly named, since it implies that LogLuv is not "Float", but the part in brackets says it is, while Wikipedia says LogLuv is NOT floating-point but fixed!
Let's for a moment assume you should keep this tab, so to fix it you should find out what each option really is, and write the correct label, and put the explanation in a tooltip:

• LogLuv TIFF (float, 16bit per color channel)
• Float TIFF (float, 32bit per color channel)

• LogLuv TIFF
tooltip: describe what it actually is, e.g. Fixed-point, L 16-bit + U 8-bit + V 8-bit, 32-bit per pixel.
• Float TIFF
tooltip: Double-precision (or single? I don't know) floating-point, 32-bit per color channel, 96-bit per pixel.

Secondly, this tab doesn't actually work. Select LogLuv as your default format, but when you save the HDR as TIFF it still defaults to 32-bit Float.

Thirdly, even if you do that, this is still not optimal. What you should do is to remove that whole tab, and instead just make the Save As window allow one to choose what they want, which is the most intuitive and easy to use way. So I would click Save-As, and then I should be able to choose:
• OpenEXR (.exr)
• Radiance RGBE (
• LogLuv TIFF (.tif)
• Float TIFF (
• PFS Stream (*.pfs)

When a user selects one of these options, the extension of the filename should get automatically corrected, e.g. if I type "foo.tif" and then I select EXR, the filename should automatically change to "foo.exr".

Saving HDR files is one of the most basic things a HDR program does, so please give this issue attention so it does that correctly.


  • Davide

    Davide - 2014-01-28
    • assigned_to: Davide
  • Davide

    Davide - 2014-01-29

    I have just pushed the changes to remove the selection of the TIFF type from the Preference Dialog. When the user wants to save the an HDR, he will receive the file dialog where it can select the format of the output file. If TIFF is selected, one further window asking the flavour (LogLuv or 32-bit float) will be use - same behaviour as 2.4.0.

  • Davide

    Davide - 2014-01-29
    • status: open --> closed
  • Beep6581

    Beep6581 - 2014-01-30

    Davide that's good. Will the wrong file extension be also fixed, so if for some reason "foo.hdr" is set as the filename, and then the user selects TIFF, will it be auto-corrected to "foo.tif"?

  • Davide

    Davide - 2014-01-30

    We are using the QFileDialog::getSaveFileName( ) to perform that action, with no customisation whatsover. We have noticed that behaviour a long time ago, but we haven't found a way to make sure that inconsistency goes away.

  • Beep6581

    Beep6581 - 2014-01-31



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