Re: [Lcms-user] Suggestions For Mixing Images With And Without Profiles
Hello Mark. Thanks for your reply and your advice. I'll look around the ColorSync mailing list to see if there is anything relevant. We have been using lcms in a cross platform application for 2 years and I totally agree with you that it is a great product. It is just this point that keeps lurking in the back of my mind so, if possible, I just want to resolve it once and for all. Regards, Kevin. From: Mark [...@cine-scan.com] Sent: 09 June 2010 14:14 To: Kevin Gale Cc: Lcms Liste Subject: Re: [Lcms-user] Suggestions For Mixing Images With And Without Profiles I actually do not agree with using Generic RGB as Apple does in Preview. IIRC Generic RGB uses almost the same primaries as sRGB, but uses a gamma 1.8 tone curve. I think assuming sources without profile are sRGB is a better choice. So I guess I'd assume it's sRGB and do a transform sRGB to monitor for display. Again, I'm sure much more experienced people than I could answer that in the ColorSync mailing list. By the way, if you are developing for the Mac only, there are some Apple APIs for transforming images between RGB color spaces. Core Image and CGImage can do it. Under Snow Leopard I think NSImage*** can too. If you need to change or create profiles, more fine grained control or a multi platform API, then LCMS is a great choice. Cheers Mark On 09.06.2010, at 09:39, Kevin Gale wrote: > Hello Mark. > > You are correct. Mac OS X Preview does assign a generic RGB profile. I must > have modified the profile in the image I was looking at and saved it without > realising. > > so... The question is should I use a generic RGB profile and use that to > transform to sRGB or just assume the data is already sRGB and do nothing. > > As we are showing the profiled pictures on-screen I guess that no matter > which way we do it the user will have a visual representation of how the > colours have been transformed and the output device will also know how to > print the data as there will be a sRGB profile attached. This must be better > than if the original unprofiled picture was printed as the output device > wouldn't know how to interpret the colours and could do anything with the > data. > > > Regards, > Kevin. > > > From: Mark [...@cine-scan.com] > Sent: 08 June 2010 21:25 > To: Kevin Gale; Lcms Liste > Subject: Re: [Lcms-user] Suggestions For Mixing Images With And Without > Profiles > > Are you sure Preview is using the monitor profile? I thought Apple uses the > Generic RGB profile when no profile is supplied - but I'm not sure. > The profile is at /System/Library/ColorSync/Profiles/Generic RGB Profile.icc > > The guys at the ColorSync mailing list might be able to answer this better... > > Mark > > > On 08.06.2010, at 20:29, Kevin Gale wrote: > >> Hi. >> >> I'm looking for some advice / thoughts on how to composite images with and >> without profiles. >> >> Some background >> >> Users can select and manipulate their digital camera pictures in our app >> on-screen before they are composited into a single file with a sRGB profile >> attached. Currently, our app does the following: >> 1. If the image has a profile the data is transformed to sRGB when >> outputting to file and to the monitor's profile for on-screen display. >> >> 2. If the image does not have a profile it assumes the data is already sRGB. >> This means that when outputting to file no transformation is performed but >> on-screen a generic sRGB profile is used as the input profile to transform >> to the monitor's profile. >> >> >> I have recently been revisiting this as I cannot decide if I am doing the >> right thing here when dealing with images that do not have a profile. For >> example, if I open an unprofiled image in Photoshop it assigns the sRGB >> profile (same result as our app) while on the other hand if I open the same >> image in Mac OS X Preview it appears to use the monitor's profile. I could >> either keep things the way they are or instead grab the monitor's profile to >> use as the input profile so that part of the composited image looks like the >> original image opened in Mac OS X Preview. >> >> Hope this makes sense so far >> >> My thoughts are that neither of these is really right or wrong since the >> image does not have any profile and the pixels are technically meaningless >> (the data could, after all, be sRGB). The end-users of our app will have no >> knowledge of profiles so to start prompting them with questions would cause >> lots of headaches. Howev
Re: [Lcms-user] Suggestions For Mixing Images With And Without Profiles
I actually do not agree with using Generic RGB as Apple does in Preview. IIRC Generic RGB uses almost the same primaries as sRGB, but uses a gamma 1.8 tone curve. I think assuming sources without profile are sRGB is a better choice. So I guess I'd assume it's sRGB and do a transform sRGB to monitor for display. Again, I'm sure much more experienced people than I could answer that in the ColorSync mailing list. By the way, if you are developing for the Mac only, there are some Apple APIs for transforming images between RGB color spaces. Core Image and CGImage can do it. Under Snow Leopard I think NSImage*** can too. If you need to change or create profiles, more fine grained control or a multi platform API, then LCMS is a great choice. Cheers Mark On 09.06.2010, at 09:39, Kevin Gale wrote: > Hello Mark. > > You are correct. Mac OS X Preview does assign a generic RGB profile. I must > have modified the profile in the image I was looking at and saved it without > realising. > > so... The question is should I use a generic RGB profile and use that to > transform to sRGB or just assume the data is already sRGB and do nothing. > > As we are showing the profiled pictures on-screen I guess that no matter > which way we do it the user will have a visual representation of how the > colours have been transformed and the output device will also know how to > print the data as there will be a sRGB profile attached. This must be better > than if the original unprofiled picture was printed as the output device > wouldn't know how to interpret the colours and could do anything with the > data. > > > Regards, > Kevin. > > > From: Mark [...@cine-scan.com] > Sent: 08 June 2010 21:25 > To: Kevin Gale; Lcms Liste > Subject: Re: [Lcms-user] Suggestions For Mixing Images With And Without > Profiles > > Are you sure Preview is using the monitor profile? I thought Apple uses the > Generic RGB profile when no profile is supplied - but I'm not sure. > The profile is at /System/Library/ColorSync/Profiles/Generic RGB Profile.icc > > The guys at the ColorSync mailing list might be able to answer this better... > > Mark > > > On 08.06.2010, at 20:29, Kevin Gale wrote: > >> Hi. >> >> I'm looking for some advice / thoughts on how to composite images with and >> without profiles. >> >> Some background >> >> Users can select and manipulate their digital camera pictures in our app >> on-screen before they are composited into a single file with a sRGB profile >> attached. Currently, our app does the following: >> 1. If the image has a profile the data is transformed to sRGB when >> outputting to file and to the monitor's profile for on-screen display. >> >> 2. If the image does not have a profile it assumes the data is already sRGB. >> This means that when outputting to file no transformation is performed but >> on-screen a generic sRGB profile is used as the input profile to transform >> to the monitor's profile. >> >> >> I have recently been revisiting this as I cannot decide if I am doing the >> right thing here when dealing with images that do not have a profile. For >> example, if I open an unprofiled image in Photoshop it assigns the sRGB >> profile (same result as our app) while on the other hand if I open the same >> image in Mac OS X Preview it appears to use the monitor's profile. I could >> either keep things the way they are or instead grab the monitor's profile to >> use as the input profile so that part of the composited image looks like the >> original image opened in Mac OS X Preview. >> >> Hope this makes sense so far >> >> My thoughts are that neither of these is really right or wrong since the >> image does not have any profile and the pixels are technically meaningless >> (the data could, after all, be sRGB). The end-users of our app will have no >> knowledge of profiles so to start prompting them with questions would cause >> lots of headaches. However, there is always the situation where I have to >> explain why the composited output from our app looks different to the >> original pictures due to the app that the original pictures were viewed in. >> >> >> Would anybody like to share their thoughts / advice on this? >> >> >> Regards, >> Kevin. >> >> E-MAIL DISCLAIMER >> The information in this email is confidential and may be legally privileged. >> It is intended solely for the addressee. Access to this email by anyone else >> is unauthorised.
Re: [Lcms-user] Suggestions For Mixing Images With And Without Profiles
Hello Mark. You are correct. Mac OS X Preview does assign a generic RGB profile. I must have modified the profile in the image I was looking at and saved it without realising. so... The question is should I use a generic RGB profile and use that to transform to sRGB or just assume the data is already sRGB and do nothing. As we are showing the profiled pictures on-screen I guess that no matter which way we do it the user will have a visual representation of how the colours have been transformed and the output device will also know how to print the data as there will be a sRGB profile attached. This must be better than if the original unprofiled picture was printed as the output device wouldn't know how to interpret the colours and could do anything with the data. Regards, Kevin. From: Mark [...@cine-scan.com] Sent: 08 June 2010 21:25 To: Kevin Gale; Lcms Liste Subject: Re: [Lcms-user] Suggestions For Mixing Images With And Without Profiles Are you sure Preview is using the monitor profile? I thought Apple uses the Generic RGB profile when no profile is supplied - but I'm not sure. The profile is at /System/Library/ColorSync/Profiles/Generic RGB Profile.icc The guys at the ColorSync mailing list might be able to answer this better... Mark On 08.06.2010, at 20:29, Kevin Gale wrote: > Hi. > > I'm looking for some advice / thoughts on how to composite images with and > without profiles. > > Some background > > Users can select and manipulate their digital camera pictures in our app > on-screen before they are composited into a single file with a sRGB profile > attached. Currently, our app does the following: > 1. If the image has a profile the data is transformed to sRGB when outputting > to file and to the monitor's profile for on-screen display. > > 2. If the image does not have a profile it assumes the data is already sRGB. > This means that when outputting to file no transformation is performed but > on-screen a generic sRGB profile is used as the input profile to transform to > the monitor's profile. > > > I have recently been revisiting this as I cannot decide if I am doing the > right thing here when dealing with images that do not have a profile. For > example, if I open an unprofiled image in Photoshop it assigns the sRGB > profile (same result as our app) while on the other hand if I open the same > image in Mac OS X Preview it appears to use the monitor's profile. I could > either keep things the way they are or instead grab the monitor's profile to > use as the input profile so that part of the composited image looks like the > original image opened in Mac OS X Preview. > > Hope this makes sense so far > > My thoughts are that neither of these is really right or wrong since the > image does not have any profile and the pixels are technically meaningless > (the data could, after all, be sRGB). The end-users of our app will have no > knowledge of profiles so to start prompting them with questions would cause > lots of headaches. However, there is always the situation where I have to > explain why the composited output from our app looks different to the > original pictures due to the app that the original pictures were viewed in. > > > Would anybody like to share their thoughts / advice on this? > > > Regards, > Kevin. > > E-MAIL DISCLAIMER > The information in this email is confidential and may be legally privileged. > It is intended solely for the addressee. Access to this email by anyone else > is unauthorised. If you are not the intended recipient, any disclosure, > copying, distribution or any action taken or omitted to be taken in reliance > on it, is prohibited and may be unlawful. All information provided, > including but not limited to, quotations, system specifications and > suggestions concerning hardware/software/services configurations are strictly > subject to our standard terms and conditions of business, copies of which are > available on request. > > > This e-mail has been scanned for all viruses by Star. The > service is powered by MessageLabs. For more information on a proactive > anti-virus service working around the clock, around the globe, visit: > http://www.star.net.uk > > > -- > ThinkGeek and WIRED's GeekDad team up for the Ultimate > GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the > lucky parental unit. See the prize list and enter to win: > http://p.sf.net/sfu/thinkgeek-promo > ___
Re: [Lcms-user] Suggestions For Mixing Images With And Without Profiles
Are you sure Preview is using the monitor profile? I thought Apple uses the Generic RGB profile when no profile is supplied - but I'm not sure. The profile is at /System/Library/ColorSync/Profiles/Generic RGB Profile.icc The guys at the ColorSync mailing list might be able to answer this better... Mark On 08.06.2010, at 20:29, Kevin Gale wrote: > Hi. > > I'm looking for some advice / thoughts on how to composite images with and > without profiles. > > Some background > > Users can select and manipulate their digital camera pictures in our app > on-screen before they are composited into a single file with a sRGB profile > attached. Currently, our app does the following: > 1. If the image has a profile the data is transformed to sRGB when outputting > to file and to the monitor's profile for on-screen display. > > 2. If the image does not have a profile it assumes the data is already sRGB. > This means that when outputting to file no transformation is performed but > on-screen a generic sRGB profile is used as the input profile to transform to > the monitor's profile. > > > I have recently been revisiting this as I cannot decide if I am doing the > right thing here when dealing with images that do not have a profile. For > example, if I open an unprofiled image in Photoshop it assigns the sRGB > profile (same result as our app) while on the other hand if I open the same > image in Mac OS X Preview it appears to use the monitor's profile. I could > either keep things the way they are or instead grab the monitor's profile to > use as the input profile so that part of the composited image looks like the > original image opened in Mac OS X Preview. > > Hope this makes sense so far > > My thoughts are that neither of these is really right or wrong since the > image does not have any profile and the pixels are technically meaningless > (the data could, after all, be sRGB). The end-users of our app will have no > knowledge of profiles so to start prompting them with questions would cause > lots of headaches. However, there is always the situation where I have to > explain why the composited output from our app looks different to the > original pictures due to the app that the original pictures were viewed in. > > > Would anybody like to share their thoughts / advice on this? > > > Regards, > Kevin. > > E-MAIL DISCLAIMER > The information in this email is confidential and may be legally privileged. > It is intended solely for the addressee. Access to this email by anyone else > is unauthorised. If you are not the intended recipient, any disclosure, > copying, distribution or any action taken or omitted to be taken in reliance > on it, is prohibited and may be unlawful. All information provided, > including but not limited to, quotations, system specifications and > suggestions concerning hardware/software/services configurations are strictly > subject to our standard terms and conditions of business, copies of which are > available on request. > > > This e-mail has been scanned for all viruses by Star. The > service is powered by MessageLabs. For more information on a proactive > anti-virus service working around the clock, around the globe, visit: > http://www.star.net.uk > > > -- > ThinkGeek and WIRED's GeekDad team up for the Ultimate > GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the > lucky parental unit. See the prize list and enter to win: > http://p.sf.net/sfu/thinkgeek-promo > ___ > Lcms-user mailing list > Lcms-user@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/lcms-user -- ThinkGeek and WIRED's GeekDad team up for the Ultimate GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the lucky parental unit. See the prize list and enter to win: http://p.sf.net/sfu/thinkgeek-promo ___ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
