Image Mosaics are assemblage of minute Images which are joined in such a way that if anyone sees the image from a distance it appears a larger image. The arrangement of small Images may be manual or automatic. In Image Mosaics color is adjusted automatically.
Creating Image Mosaics follows the following steps:
• Choosing an image: Choice depends on the person who is performing the Image Mosaics or the purpose of Image Mosaics . Juxtapositioning Images at various scales is one of the attractive feature of Image Mosaics . Another factor is distribution of colors. Uniform distribution of colors in Images are more suitable for Image Mosaics .
• Finding a tilling pattern: Keeping in mind about the type of tilling to be used in the Image Mosaics , the image tiles can be arranged. The simplest pattern is semiregular rectangular grids. For traditional halftoning, hexagonal grids are used. The pattern which matches the given target image best is the most suitable target pattern. The image tiles after being arranged in a rectangular grid have the same aspect ratio.
• Arranging the image tiles: After the grid of tilling have been selected, the tiles can be arranged in different ways for creating Image Mosaics
• Using equivalent tiles everywhere
• Image tiles can be arranged randomly
• Manual arrangement of various tiles through eye
• Tiles can be placed in the regions of target image by matching the colors.
• After matching both shape and color, the tiles may be arranged in the tilling grid.
• Color correction: After the arrangement is over, color correction is the next step towards Image Mosaics . The colors of the tile Images are altered to match the target images . A shifting and scaling rule is used for color correction in Image Mosaics .
Image Mosaics in Geography Information Systems (GIS )
Image Mosaics can be done in GIS by mosaicking the different imageries produced by satellites, aerial photography and digital cameras. Orthorectification is the traditional approach used for Image Mosaics in GIS.
Two types of Image Mosaics are found in GIS:
• Non-georeferenced Image Mosaics : Here Image Mosaics are done by simple matching the sides of the photographs. Georeferencing is not done in this kind of image, so image coordinates cannot be transferred to map Images.
• Georeferenced Image Mosaics : The Images are arranged based on the georeferencing information given on the reference image. As a result image coordinates can be transformed to map Images.
Advantage of Image Mosaics in GIS:
• Management of image files is easier for Image Mosaics in GIS. Processing and analyzing one large image is easier than numerous small Images. These large files are better controlled and managed by personal computers.
• Image Mosaics can be analyzed and classified in much better way by GIS user as it provides a better method of interpretation.
Thus Image Mosaics are important tool in GIS which provides a number information and as a result it can be easily interpreted. Different softwares like Digital Imagery Made Easy is now available which has made creation of Image Mosaics in GIS easy.
Image Mosaics are thus used by artists, painters and also by GIS professionals.