A method of increasing contrast of an image, the method comprising: receiving an image in a first color space, the image having been captured by a swallowable capsule comprising an imager for obtaining images from inside a body lumen; mapping pixel color characteristics of the image to a second color space; obtaining a color distribution of the image in the second color space; determining an original mean value of the color distribution of the image in the second color space; determining a new mean value in the second color space, the new mean value being determined based on a predetermined value; calculating new pixel color characteristics in the second color space with the following equation: New_uʹ = uʹ - u ̅ ⋅ ScaleFactor + New_u ̅ New_vʹ = vʹ - v ̅ ⋅ ScaleFactor + New_v ̅ wherein u and v denote the original mean values in the second color space; New_u and New_v denote the new mean values in the second color space; New_u' and New_v' denote the new pixel color characteristics in the second color space; u' and v' denote the original pixel color characteristics in the second color space; and ScaleFactor denotes a selected scaling factor; and wherein luminance is kept constant; and constructing a color-expanded image in the first color space by transforming the new pixel color characteristics calculated in the second color space into new pixel color characteristics in the first color space. receiving an image in a first color space, the image having been captured by a swallowable capsule comprising an imager for obtaining images from inside a body lumen; mapping pixel color characteristics of the image to a second color space; obtaining a color distribution of the image in the second color space; determining an original mean value of the color distribution of the image in the second color space; determining a new mean value in the second color space, the new mean value being determined based on a predetermined value; calculating new pixel color characteristics in the second color space with the following equation: New_uʹ = uʹ - u ̅ ⋅ ScaleFactor + New_u ̅ New_vʹ = vʹ - v ̅ ⋅ ScaleFactor + New_v ̅ wherein u and v denote the original mean values in the second color space; New_u and New_v denote the new mean values in the second color space; New_u' and New_v' denote the new pixel color characteristics in the second color space; u' and v' denote the original pixel color characteristics in the second color space; and ScaleFactor denotes a selected scaling factor; and wherein luminance is kept constant; and constructing a color-expanded image in the first color space by transforming the new pixel color characteristics calculated in the second color space into new pixel color characteristics in the first color space. u and v denote the original mean values in the second color space; New_u and New_v denote the new mean values in the second color space; New_u' and New_v' denote the new pixel color characteristics in the second color space; u' and v' denote the original pixel color characteristics in the second color space; and ScaleFactor denotes a selected scaling factor; and wherein luminance is kept constant; and constructing a color-expanded image in the first color space by transforming the new pixel color characteristics calculated in the second color space into new pixel color characteristics in the first color space.