The following file formats can be analysed with Hemisfer:
Files with either 2, 8 or 24 bits per pixel can be analysed, i.e. 2, 256 or 16 million colours. If you have other file formats to analyse, it is recommended to transform them beforehand to one of the accepted formats. Irfan View is a nice, powerful, easy-to-use tool to do this. It is free for private, non-commercial use.
According to our tests, a high-quality JPEG file will give practically the same results as an uncompressed file. This format can thus be recommended for pictures taken with a digital camera, with the advantage to keep all the information about the picture within the file (EXIF, IPTC and/or JPEG comments). Be sure to allow for a tolerance if you use a colour to be ignored with a JPEG file. Otherwise, this colour will not be correctly recognised due to the inaccuracy of the file compression. With a good-quality JPEG, a tolerance of 40 can generally be recommended.
A TIFF format can be obtained from some cameras and from most scanners used to scan films (or a slides). A loss-less TIFF compression appears in some reports to be better than even high-quality JPEG.
Better cameras offer also the possibility to save pictures in a proprietary raw format. In such a case, the manufacturers deliver a software to extract JPEG pictures from the raw format, with the possibility of some tuning on the exposure. Raw files are larger and take thus more disk space, but they save the entire original information of the picture and can thus be recommended to retain the possibility of any further processing.
GIF is recommended for pictures in grey tones, where its maximum of 256 colours is not limiting. Converting colour pictures to grey tones before analysis with Hemisfer is an efficient way to save disk space (and analysis time). It means, however, that the colour channel weights must be decided at this point.