Geo-referenced image format
g-Space supports tiff, png, jpg, bmp formats coupled with world files. World files contain information about X and Y for each pixel of the image.
World file has 6 parameters:
•Line 1: A: x-component of the pixel width (x-scale)
•Line 2: D: y-component of the pixel width (y-skew)
•Line 3: B: x-component of the pixel height (x-skew)
•Line 4: E: y-component of the pixel height (y-scale), typically negative
•Line 5: C: x-coordinate of the center of the original image's upper left pixel transformed to the map
•Line 6: F: y-coordinate of the center of the original image's upper left pixel transformed to the map
File example:
They must have same names as image files but different extensions and located in the same directory. Extensions have firs two characters of image file extension and additional 'w' at the end.
For more information can be found here World file - Wikipedia.