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I have a black and white JPEG. It is in fact an RGB image, which means that the color is still there. And I know from past experience that when I shoot B&W with my Canon, the color image is still retained. So, how can I restore that color to its proper shape, so to speak? I tried using Bridge and opening it within the RAW window, but there's no obvious tool therein to open it in color. Any suggestions welcome.

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If this image were RAW, the color would still be there. But since it is JPEG, I'm afraid not. The fact that the image is in RGB format does not help, because I'd you look, you will find that in fact for each pixel, each of these values is set to the same thing: (0,0,0), (37,37,37), (221,221,221), or whatever. That is, they're all gray levels, just represented in RGB triplets.

When the image was converted to back and white, all colors were mapped to single gray levels, and the original color information indeed irreversibly lost.

You could convert the image to true grayscale JPEG, and I think pretty much any program would be able to render that (although some weird devices may only understand the much more common RGB). This will save some space, but since JPEG is compressed anyway, not as much as you might think. And of course this won't help your reversal wish.

Your only options here are to find the original, or to paint in false color (as if you are desecrating an old movie).

  • Canon RAW files include all the colour information. If the photo is taken in black and white mode, there's an entry in the RAW that says, "And display this in black and white, please." – David Richerby Aug 22 '15 at 0:26
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    @David That is the case with every RAW format, not just Canon. Except of course the few cameras with monochrome sensors. – mattdm Aug 22 '15 at 0:29
  • @mattdm ... I have the same issue; a photograph that was taken with the B&W profile, and is a JPEG . BUT , every time I open it you can see briefly the photo in color; then it transform into black&white. Is just less than a second; but the color is there. The only thing is that there is something that tells to the photo " hey you must be in black & white" ; so I am sure there must be a way to get the color info back. It was taken with one of those Canon non-dslr, small ones, and around few years back. – Davinci White Mar 6 '17 at 18:35
  • @DavinciWhite What software are you viewing your image with? Can you post it somewhere? I'd be curious to look. The normal JPEG format has no such conversion metadata. It's possible that it's a specially-constructed image doing something creative with image interleaving as in this answer, but that seems unlikely. – mattdm Mar 6 '17 at 20:31
  • The flash of colour you're seeing will be the 'preview image', which may well be colour but it is also low-res (so not useful for recovery). – James Snell Mar 8 '17 at 7:56
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Unfortunately, a JPEG is a one-way, destructive process. It may be RGB, but it no longer contains the colors originally present, only those written in the B&W conversion process.

If you had the RAW (.CR2) file, however, you could recover the colors. Think of the RAW file as a master, and JPEGs are created from that.

  • I do not agree on the part JPEG is one way destructive process. It has nothing to do that a image is jpg with the fact it is a grayscale image. I understand that you say that starting from a RAW file. But no one is saying that has the original RAW file either. ;o) – Rafael Aug 21 '15 at 18:50
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    @Rafael JPEG is a destructive process - it's a lossy compression method, which in this case is the same thing as a one-way method: it's impossible to un-do it - granted, there are other such methods, with different names, but if the result is the same, it's a destructive process. – user2813274 Aug 22 '15 at 0:08
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    @user2813274 Sure, JPEG is destructive. But the destruction here isn't because the image was saved as a JPEG: you wouldn't be able to recover the colour information if it had been saved as a TIFF or a PNG, instead. It's the destructive nature of the B/W conversion that's the problem; the fact that the result of that converseion was stored as a JPEG is almost irrelevant. – David Richerby Aug 22 '15 at 0:24
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Since you only have a black and white JPG there is no "color" information there. There is only shades of gray, "color" is lost.

There is no 100% automated process to do this for you, you ll have to use a software to perform something like this:

To perform digital colorization, a digitized copy of the best monochrome film print available is needed. Technicians, with the aid of computer software, associate a range of gray levels to each object, and indicate to the computer any movement of the objects within a shot. The software also is capable of sensing variations in the light level from frame to frame and correcting it if necessary. The technician selects a color for each object based on (1) common "memory" colors such as blue sky, white clouds, flesh tones and green grass, and (2) based on any known information about the movie. For example, if there are color publicity photos or props from the movie available to examine, authentic colors may be applied. (3) In the absence of any better information, the technician chooses a color that fits the gray level and that the technician feels is consistent with what a director might have chosen for the scene. The computer software then associates a variation of the basic color with each gray level in the object, while keeping intensity levels the same as in the monochrome original. The software then follows each object from frame to frame, applying the same color until the object leaves the frame. As new objects come into the frame, the technician must associate colors to each new object in the same way as described above.[5] This technique was patented in 1991.[6]

source: https://en.wikipedia.org/wiki/Film_colorization#Digital_colorization

Of course the above quote is for video, but you can get the idea about what you'll expect from a colorization software to use on a photo. Some presets about sky, grass, flesh etc. but mostly you'll have to choose manually a color that "fits", on objects that you'll have to select precisely. A reference colored photo would be helpful.

A quick googling got me this software, which seems to fits your needs (but im pretty sure there are others too)

https://www.youtube.com/watch?v=RNC0JQUevbM

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