Histogram
Color
is one of the features that can be used in image retrieval system. Color can be
represented in the form of a histogram. Color histogram represents the
distribution of the number of pixels for each intensity colors in the image. To
define the histogram, each color quantize into some discrete level. For each level
the number of pixels is calculated according to the value as shown in Figure below
Horizontal axis represent color levels of the pixels in image
and vertical axis express pixel numbers in each appropriate color level.
Histogram
Distance
Color
composition similarity of images can be
determined by its color histogram. Level of similarity between two images
measured with its histogram distance. If
G = {g1,
g2, . . . , gN } and H = {h1, h2,
. . . , hN } are
the color histogram from two images, where gi and hi
is the number of pixels at level i
and N
is the number of levels for each histogram, then distance (d) between two histogram can be expressed in Manhattan metric as in
equation :
Image with smaller distance value is considered has more
similar color compared with image that has greater distance value.
