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Glitch in greyscale histogram

PostPosted: Tue Feb 21, 2012 11:08 pm
by chrisjj
I'm finding some images with smooth histograms in all channels e.g.

Image

when converted to greyscale show a glitch e.g.

Image .

Any ideas?

Re: Glitch in greyscale histogram

PostPosted: Wed Feb 22, 2012 9:46 am
by andrew.kirillov
It may have something to do with numerical rounding in grayscale filter.

If you would like you may create a ticket in issue tracking system - potentially it may be resolved. But if you do so, you will need to specify version of the software you use and preferably attach sample image which demonstrates the issue.

Re: Glitch in greyscale histogram

PostPosted: Sat Feb 25, 2012 10:19 pm
by chrisjj
OK, thanks. This image is project confidential but I'll post a report when I see the bug on one that isn't.

But I must say rather than a fix to this, I would like a fix to File Open converting my greyscale image to RGB. It is only becasue I have to use IPLab to convert it back to gray sacel that I have this current problem.

Re: Glitch in greyscale histogram

PostPosted: Sun Feb 26, 2012 10:30 am
by andrew.kirillov
chrisjj wrote:I would like a fix to File Open converting my greyscale image to RGB

You are welcome to do this if you find the way how.

1) The conversion may be actually done by .NET, not IPLab. If so, there is not much to do about it.
2) What is format of your image? PNG? JPEG? ets? What is pixel format of it? 8 bpp, or 24 bpp, or?

Re: Glitch in greyscale histogram

PostPosted: Sun Feb 26, 2012 12:05 pm
by chrisjj
> 1) The conversion may be actually done by .NET, not IPLab.

Self-evidently it is being done by IPLab, since it is IPLab that implements the File | Open command responsible. But perhaps IPLab is using a .NET call which does the conversion and taking no action to remedy this.

> 2) What is format of your image? PNG? JPEG? ets? What is pixel format of it? 8 bpp, or 24 bpp, or?

8bpp PNG.

Re: Glitch in greyscale histogram

PostPosted: Sun Feb 26, 2012 2:53 pm
by andrew.kirillov
chrisjj wrote:8bpp PNG.

.NET does not care about 8 bpp PNG and Bitmap.FromFile() loads them as 32 bpp images.

Re: Glitch in greyscale histogram

PostPosted: Sun Feb 26, 2012 4:16 pm
by chrisjj
Well, I care about 8bpp greyscale and evidently IPLab does too, so I think IPLab should take a little more care in loading them.