Segmenting multi bands images by color and texture Eldman O. Nunes - IC - UFF Aura Conci Introduction •Use of fractals and image multiespectral bands to characterize texture. •Considering inter-relation among bands the image FD є [ 0 , number of bands + 2] . •Improve the possibilies of usual false color segmentations (assigning satellite bands to RGB color). It is not now limited to 3 band. • The color sensations noticed by humans are combination of the intensities received by 3 types of cells cones. • Combination of the 3 primary colors produces the others • In the video: R=700 nm, G = 546,1 nm, B=435,1 nm. Digital images Monocromatic : one color channel or one band. • binary image: each pixel only 0 or 1 values. • intensity level (grey level): each pixel one value from 0 to 255. • Multiband images: n band value for each pixel. • examples: »color images »sattelite images »medical images color images each pixel 3 values ( from 0 to 255 ) 3 bands: Red - Green -Blue. Band 1 Band 2 Band 4 Band 5 Band 3 Band 6 Band 7 example : a LandSat-7 image is a collection of 7 images of same scene sensor TM characteristics HRV AVHRR spacial resolution 30 m 120 m (Band 6) 20 m (Band 1 a 3) 10 m (Pan) 1.1 Km (nominal) spectral Bands (micro meters) Band 1 - 0.45-0.52 Band 2 - 0.52-0.60 Band 3 - 0.63-0.69 Band 4 - 0.76-0.90 Band 5 - 1.55-1.75 Band 6 - 10.74-12.5 Band 7 - 2.08-2.35 Band 1 - 0.50-0.59 Band 2 - 0.61-0.68 Band 3 - 0.79-0.89 Pan - 0.51-0.73 Band Band Band Band Band Radiometric resolution 8 bits 8 bits (1-3) 6 bits (Pan) 10 bits 16 days 26 days 2 times a days Temporal resolution 1 - 0.58-0.68 2 - 0.725-1.1 3 - 3.55-3.93 4 - 10.30-11.30 5 - 11.50-12.50 Landsat 7 - Sensor TM Channel spectral band (um) main applications 1 0.45 - 0.52 Differentiation between soil and vegetation, conifers and deciduous trees 2 0.52 - 0.60 healthy vegetation 3 0.63 - 0.69 chlorophyll absortion, vegetation types 4 0.76 - 0.90 biomass , water bodies 5 1.55 - 1.75 penetrate smokes, snow 6 10.4 - 12.5 surface temperature from -100 to 150 C 7 2.08 - 2.35 hidrotermal map, buildings, soil trafficability Multiespectral false color : l , m, n Bands to Red, Green and Blue. Band 4 (R), 5 (G), 3 (B) Band 4 (R), 3 (G), 2 (B) Textures Texture is characterized by the repetition of a model on an area. Textons : size, format, color and orientation of the elements. Textons can be repeated in an exact way or with small variations on a same theme. Texture 1 Texture 2 Fractal Geometry • self similar sets • fractal dimensions and measures used to classify textures FD for binary image • Box Counting Theorem - 2D images. • For a set A, Nn(A) = number of boxes of side 1/2n which interser the set A: DF = lim n log Nn (A) / log 2n n Nn (A) 2n log Nn (A) log 2n 1 4 2 1,386 0,693 2 12 4 2,484 1,386 3 36 8 3,583 2,079 4 108 16 4,682 2,772 5 324 32 5,780 3,465 6 972 64 6,879 4,158 log Nn (A) 8 6 4 2 0 0 1 2 3 log (2n ) 4 5 gray level images • Box Counting Theorem extension for 3-dimensional object: third coordinate represents the intensity of the pixel. • DF between 2 e 3. Blanket Dimension - Blanket Covering Method The space is subdivided in cubes of sides SxSxS ’. Nn(A) denotes the number of cubes intercept a blanket covering the image: Nn = nn (i,j) On each grid (i,j), nn (i,j) = int ( ( max – min ) / s’ ) + 1 for multi-bands image •a color R G B image is a subset of the 5-dimensional space : N5). Each pixel is defined by: (x, y, r, g, b) •FD of this images: values from 2 to 5. Generalizing: d-cube • points (0D), segments (1D), squares (2D), cubes (3D) and • for a n-dimensional : n-cube (nD) • But what is d-cubos , and how many d-cubes appear in a divison of Nd space? r r r r r r SEGMENTO QUADRADO CUBO Sweep representation : • n-cube as translational swepps of (n-1) cube Generalizing: d-Cube Counting - DCC: • the experimental determination of the fractal dimension of images with multiple channels; • will imply in the recursive division of the N space in d-cubes of size r; • followed by the contagem of the numbers of d-cubes that intercept the image. the space N3 is divided by 3-cubos of size 1/2n, and the number of 3cubos that intercept the image it is counted. • monochrome images: • color images: the space N5 is divided by 5cubos of the same size 1/2n, and the number of 5-cubos that intercept the image is counted. • satellite images: the space Nd is divided by dcubes of size 1/2n and the number of d-cubes that intercept the image is counted. • number of 1-cubes: Nn 1-cubos = 2 1x n, where n is the number of divisions. • number of 2-cubes: Nn 2-cubos = 2 2x n, where n is the number of divisions. • number of 3-cubos: Nn 3-cubos = 2 3x n, where n is the number of divisions. • Generalizing, the number of identical d-cube: Nn d-cubes = 2 d x n, where d is the space dimension and n it is the number of divisions. Then FD of d-dimensional images can be obtained by: DFn = log (Nn,d-cubo) /log (2n ) Results binary images gray scale colored images satellite images CDC invariance to resolution (FD 3,465) CDC invariance on colors reflection (second image) and affine transformations (FD 3,465) CDC invariance to band combinations(FD 3,465) : RGB (4-5-6, 4-6-5, 5-4-6, 5-6-4, 6-4-5, 6-5-4) Mosaic of textures: original x CDC Segmentation result: same color means same texture. comparison: original SPRING - SEGWIN CDC Region on the city of Patriocínio - MG (from Landsat 5-TM, 5-4-3 spectral band to RGB) Segmentation results by CDC