Questions and postings pertaining to the usage of ImageMagick regardless of the interface. This includes the command-line utilities, as well as the C and C++ APIs. Usage questions are like "How do I use ImageMagick to create drop shadows?".
After converting, the image's colorspace is still CMYK.
Other photos could be convert successfully, only this photo failed.
How to convert the "sepecial" photo ?
You can convert the pictures that way only if in the file is already the correct source color profile. If there's no embedded source color profile, you have to specify it manually (for CMYK pictures in such cases, use a generic SWOP profile, or e.g. "US Web Coated SWOP"). So, you have to use something like this:
convert file_4.jpg -profile USWebCoatedSWOP.icc -profile SRGBSPAC.ICM 1.jpg
See also here for more about the color profiles: http://www.imagemagick.org/Usage/formats/#color_profile