Do you literally mean moving the iOS simulator window to a different monitor, even though there’s never a display context in any of this code?
-- Rick Mann rm...@latencyzero.com > On Nov 16, 2017, at 19:55, Alex Zavatone <z...@mac.com> wrote: > > I was basing my assumption on this line of your email: > >>>> 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. > > In that, I was assuming that the image from the CGImage that you mention is > similar should be the same. > > My guess here is that the PNG that you saved has a colorspace applied to it. > But it seems odd that the bytes are different unless the image is run through > a transform with CI. I wouldn’t expect one either. > > About 3 years ago when I was looking into similar things, I came across a > nice explanation of the CI pipeline, in the Apple Docs that did a good job > explaining what happens where and when. Even in the display of image items > that are saved/loaded to/from disk. > > Everything came down to not accommodating the color profile or something > related to that. > > I even got different results when testing on 2 monitors. > > An easy way to rule out my hypothesis would be to check the results on two > different displays with different color calibration and see if that has some > effect or no effect at all. > > > A quick walk through the CI pipeline docs will probably trigger something > that will answer your question. > > I’ll see it I can find the ones that were useful to me for you. > > > > > > >> On Nov 16, 2017, at 9:29 PM, Rick Mann <rm...@latencyzero.com> wrote: >> >> OpenCV is not relevant in this case, that was just background that I >> probably didn't need to include. >> >> I'm generating an image buffer, saving it as PNG through UIImage, then >> generating it again, and comparing it to the UIImage bytes I get by opening >> the previously-saved image. I'm not specifying anything other than device >> RGB color space when I create the CGBitmapContext I use to generate the >> image buffer. >> >>> On Nov 16, 2017, at 19:27 , Alex Zavatone <z...@mac.com> wrote: >>> >>> 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 <rm...@latencyzero.com> 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 >>>> rm...@latencyzero.com >>>> >>>> >>>> _______________________________________________ >>>> >>>> Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) >>>> >>>> Please do not post admin requests or moderator comments to the list. >>>> Contact the moderators at cocoa-dev-admins(at)lists.apple.com >>>> >>>> Help/Unsubscribe/Update your Subscription: >>>> https://lists.apple.com/mailman/options/cocoa-dev/zav%40mac.com >>>> >>>> This email sent to z...@mac.com >>> >> >> >> -- >> Rick Mann >> rm...@latencyzero.com >> >> > _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
