Legacy ImageMagick Discussions Archive

Before to export my image to the web, i want to convert them to sRGB and then remove the sRGB profile from the image (to reduce it's size as sRGB is the default profile to use if their is no embed icc profile). I was thinking that their is only one sRGB icc profile but i discover their is many variants ! for example on color.org their is sRGB v4 (with is included in distribution of imagemagick) and sRGB v2

So with sRGB profile i need to choose to convert my picture for exporting to the web? why so many different sRGB profiles (https://ninedegreesbelow.com/photograph ... rison.html) ?

I'm not sure what you are asking. In the article you cite, Elle Stone explains the differences between the profiles, and how they have arisen.

If you embed the profile in your image (which Elle recommends) then I suggest that you use v2 as some software can't read v4.

If you strip the profile, then it doesn't matter if you use v2 or v4.

thanks snibgo !

I discover i don't know too much about icc

maybe i can explain what i m worry :

I have a webserver that store image (like instagram or 500px). some of theses image come from iphone 7+ and have an embed icc profile (P3). but most of the android device have no color management and support only sRGB.

So here i m, i was naively thinking that i simply need to convert image with embed icc profile other than sRGB (like P3) to sRGB, store both version on the server, send icc version to iphone7+ and sRGB version to android and voila ... but I discover that their is many sRGB icc profile available so with do choose ? the one from color.org? the one from photoshop? other ? and now i even ask myself, do i really need to convert the image ? what actually the conversion will do ?

For the widest viewability across devices, sRGB is the best choice.

Yes, there are different varieties of sRGB. Converting to a profile and embedding that profile means you have specified the exact colours that should be displayed. If you don't embed, client software will assume sRGB and will apply its own version of sRGB, so results will be variable across different devices.

This is why Elle recommends that, whichever sRGB profile is used, it should be embedded, not stripped.

Elle's argument is sound. However, most consumer devices are not calibrated, so results will vary anyway, however much care we take to embed the correct profile. I think Elle's approach is most suitable for the few clients who have calibrated screens, with software that correctly uses the calibration.

My "snibgo's IM pages" website has many small images, and the exact colours displayed don't matter, and download speed does matter, so I usually don't embed profiles. Besides, my monitor isn't calibrated, so I don't see the exact colours that profile says I should see, so I never know what colours clients will see even if I do embed.

If your monitor is calibrated, and you care that your clients see the same colours as you do, you should embed the profile. Which sRGB profile? As Elle says, there is little practical difference. For maximum compatibility, she recommends her own sRGB-elle-V2-srgbtrc.icc (see https://ninedegreesbelow.com/photograph ... files.html).

thanks snibgo, i start to see a little better now

Last question, android device < 0 can't handle icc profile (that a shame). What would you suggest to me ? Store the picture on the server in both variant, I mean with icc profile embed and without icc profile embed where i first make the conversion to sRGB-elle-V2-srgbtrc.icc and then strip off the icc profile ? in this way i can send to android device the picture in sRGB without any icc.

But As far as i see the iphone 7 picture with P3 icc profile are not so bad when viewing in non color managed device, so do i really need to convert them to sRGB ? but i don't test very much and as i say i m even not sure if the conversion to sRGB-elle-V2-srgbtrc.icc will make them better. also storing the picture in both variant mean much more storage space will be necessary

loki5100 wrote:Last question, android device < 0 can't handle icc profile (that a shame).

Do you mean android simply ignores the ICC profile, or that it refuses to display the image? If it simply ignores the profile and assumes the image is sRGB, then embedding an sRGB profile is harmless. But ignoring the profile of an image coded in P3 will result in washed-out colours.

What is your general audience? If the greatest colour precision is needed, then you should embed profiles.

P3 has a significantly wider gamut than sRGB (mostly in the greens). For general web consumption, I think you should convert P3 images to sRGB. But if you know that your audience often have devices with wider gamut than sRGB, then limiting your images to sRGB would be a shame.

Do you mean android simply ignores the ICC profile, or that it refuses to display the image?

yes android simply ignore icc profile it's show the image like if no embed icc profile was present

If it simply ignores the profile and assumes the image is sRGB, then embedding an sRGB profile is harmless.

Yes but i don't know maybe it's stupid, but i think that if i convert the image to sRGB (even if i remove the sRGB profile later) then i will have better color no ?

P3 has a significantly wider gamut than sRGB (mostly in the greens). For general web consumption, I think you should convert P3 images to sRGB. But if you know that your audience often have devices with wider gamut than sRGB, then limiting your images to sRGB would be a shame.

That why i would like to know: does converting the P3 image to sRGB will produce better (or worse) image than simply letting android ignoring the icc profile ? as i know when a color is out of the gamut then the most closest color will be used. So is it really matter to convert the image and store it in P3 and sRGB ?

loki5100 wrote:That why i would like to know: does converting the P3 image to sRGB will produce better (or worse) image than simply letting android ignoring the icc profile ?

If an image is encoded as P3 with embedded P3 profile but android ignores the profile and assumes the image is sRGB, then it will display the wrong colours. They will be washed out (the saturation will be too low).

Instead, you can convert the image to sRGB and send that to android, and it will display reasonable colours, not washed out.

thanks snibgo ! so i decide to store the image in the server in 2 variants: one with icc profile given at the upload time (even if it's sRGB as their is many sRGB variant) and one converted to the sRGB.icc profile (and to with i will strip of the sRGB icc profile as android will simply not read it)

After to know is a device/monitor is able to display correctly such profile (like P3) that another story ...

you help me a lot ... I already have im.snibgo.com in my fav, very good imagemagick blog !

by the way doing this we must absolutely not use the sRGB.icc profile located in imagemagick, It's produce very different and completely washed out image when the image is showed on android or non color managed software (who ignore the icc)

@snibgo, i have another question, do you know what is MagickSetImageColorspace ? i m a little lost to understand the difference with Icc profile do i need to worry about image color space ?

When the image has profiles, you generally should not use MagickSetImageColorspace().

(There are exceptions. An image with a profile may have channels representing red, green and blue, and we might temporarily convert these to hue, chroma and lightness for some purpose.)

but if i convert say a CMYK image with icc profile to sRGB icc profile, then do i need to keep the image color space in CMYK ?

If you have a CMYK image with embedded CMYK profile, then converting to an sRGB profile will automatically change the colorspace.

@snibgo ... exact i just try it so no need to call MagickSetImageColorspace

thanks !