Re: Avoiding color transformations in PNG/UIImage/CGImage ops?
Re: Avoiding color transformations in PNG/UIImage/CGImage ops?
- Subject: Re: Avoiding color transformations in PNG/UIImage/CGImage ops?
- From: Alex Zavatone <email@hidden>
- Date: Thu, 16 Nov 2017 21:27:24 -0600
Before looking into OCV, my wild guess is that it may have to do with the
colorspace of the image. What are you setting it to? Profile Name: sRGB
IEC61966-2.1?
> On Nov 16, 2017, at 8:31 PM, Rick Mann <email@hidden> wrote:
>
> I'm trying to write a unit test for some code I wrote that generates one
> image from another. In the main app, the source data comes from Open CV as a
> buffer of 3 byte-per-pixel elements. My code generates a CGImage. In the unit
> test, I load a saved version of one of those images from a PNG file to
> UIImage, get at the buffer, pass it to my code, and then compare the result
> to a saved version of that same output.
>
> The saved version is a PNG. I load that, and then get the data buffer using
>
> let fiData = fi.dataProvider?.data as Data?
>
> I do a similar thing with the generated CGImage. Then I compare the two
> buffers, byte by byte. They are similar, but contain differences (sometimes
> more than I would expect). But if I save both as PNG and look at them in
> Preview they look identical.
>
> My guess is something's happening somewhere with color correction. In my
> code, I make a CG(bitmap)Context, specifying device RGB color space (should
> that be generic?). I don't really know what happens to the PNGs I save and
> load.
>
> Is there a way to ensure the bytes in the buffer are compressed and
> decompressed exactly as written?
>
> --
> Rick Mann
> email@hidden
>
>
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