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A New Image Compression Scheme Based on Locally Adaptive Coding. Chair Professor Chin-Chen Chang Feng Chia University. Introduction. Image compression technique. w. h. Image. Index table. Vector Quantization Encoder. Introduction (Cont.). Image compression technique. w. h. Image.
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A New Image Compression Scheme Based on Locally Adaptive Coding Chair Professor Chin-Chen Chang Feng Chia University
Introduction Image compression technique w h Image Index table Vector Quantization Encoder
Introduction (Cont.) Image compression technique w h Image Index table Vector Quantization Decoder
Introduction (Cont.) VQ Histogram Index table Image
Locally adaptive scheme Introduction (Cont.) • Ex: a a b b c a c a b d c c e f b a List List b a a 0 0 1 … List List List List c c c a b a b a b c b a 002 012 102 002 012 102 002 012 102 002 012 102 0a100b100c110101101… 1: index existed in list 0: the symbol does not exist in list • Concept: Moving the Recently Used to the Front
The Proposed Method Divide the temporary codebook into two Parts (frequently-used and infrequently-used) Refine the frequently-used part of temporary codebook Divide image into non-overlapping blocks Generate temporary codebook Image I Refine the infrequently-used part of temporary codebook generated codebook Output Compress I by referencing the generated codebook Compression code
The Proposed Method (Cont.) • The proposed method includes two phases for codebook generation • Temporary codebook generation • Codebook refining
Temporary Codebook Generation • The codebook generation is based on the concept of locally adaptive coding Temporary Codebook w Bi = {84, 170, 166, 167, 83, …, 168} G1 = { g1,1={199, 96, 84, 167, 83, …, 130}, g1,2={201, 97, 90, 167, 85, …, 132}, g1,3={200, 95, 82, 167, 81, …, 131}} h G2 = { g2,1={84, 170, 166, 167, 84, …, 170}, g2,2={86, 168, 165, 170, 90, …, 165}} G3 = { g3,1={184, 83, 194, 170, 166, …, 110}, g3,2={180, 80, 194, 166, 168, …, 114}, g3,3={185, 85, 190, 172, 160, …, 120}, g3,4={191, 88, 197, 170, 162, …, 107}} ∵d(Bi , g2,1) = 2.24 TH = 25 ∴ add Bi into G2 and move G2 to be the first one Image Gn = { gn,1={244, 83, 174, 210, 166, …, 127}, gn,2={243, 80, 175, 213, 168, …, 128}, gn,3={240, 85, 176, 209, 160, …, 126}, gn,4={244, 88, 178, 213, 162, …, 127}} *d(•): Euclidean distance function
Temporary Codebook Generation (Cont.) Temporary Codebook Temporary Codebook G1 = { g1,1={199, 96, 84, 167, 83, …, 130}, g1,2={201, 97, 90, 167, 85, …, 132}, g1,3={200, 95, 82, 167, 81, …, 131}} G2 = { g2,1={84, 170, 166, 167, 84, …, 170}, g2,2={86, 168, 165, 170, 90, …, 165}, g2,3={84, 170, 166, 167, 83, …, 168}} G2 = { g2,1={84, 170, 166, 167, 84, …, 170}, g2,2={86, 168, 165, 170, 90, …, 165}, g2,3={84, 170, 166, 167, 83, …, 168}} G1 = { g1,1={199, 96, 84, 167, 83, …, 130}, g1,2={201, 97, 90, 167, 85, …, 132}, g1,3={200, 95, 82, 167, 81, …, 131}} G3 = { g3,1={184, 83, 194, 170, 166, …, 110}, g3,2={180, 80, 194, 166, 168, …, 114}, g3,3={185, 85, 190, 172, 160, …, 120}, g3,4={191, 88, 197, 170, 162, …, 107}} G3 = { g3,1={184, 83, 194, 170, 166, …, 110}, g3,2={180, 80, 194, 166, 168, …, 114}, g3,3={185, 85, 190, 172, 160, …, 120}, g3,4={191, 88, 197, 170, 162, …, 107}} Gn = { gn,1={244, 83, 174, 210, 166, …, 127}, gn,2={243, 80, 175, 213, 168, …, 128}, gn,3={240, 85, 176, 209, 160, …, 126}, gn,4={244, 88, 178, 213, 162, …, 127}} Gn = { gn,1={244, 83, 174, 210, 166, …, 127}, gn,2={243, 80, 175, 213, 168, …, 128}, gn,3={240, 85, 176, 209, 160, …, 126}, gn,4={244, 88, 178, 213, 162, …, 127}}
Temporary Codebook Generation (Cont.) Temporary Codebook w G2 = { g2,1={84, 170, 166, 167, 84, …, 170}, g2,2={86, 168, 165, 170, 90, …, 165}, g2,3={84, 170, 166, 167, 83, …, 168}} Bj = {220, 212, 182, 179, 240, …, 246} h G1 = { g1,1={199, 96, 84, 167, 83, …, 130}, g1,2={201, 97, 90, 167, 85, …, 132}, g1,3={200, 95, 82, 167, 81, …, 131}} G3 = { g3,1={184, 83, 194, 170, 166, …, 110}, g3,2={180, 80, 194, 166, 168, …, 114}, g3,3={185, 85, 190, 172, 160, …, 120}, g3,4={191, 88, 197, 170, 162, …, 107}} Image Gn = { gn,1={244, 83, 174, 210, 166, …, 127}, gn,2={243, 80, 175, 213, 168, …, 128}, gn,3={240, 85, 176, 209, 160, …, 126}, gn,4={244, 88, 178, 213, 162, …, 127}} ∵ No any block satisfies d(Bj, gk) TH = 25 ∴ Create a new group Gn+1, add Bj into Gn+1, and move Gn+1 to be the first one
Temporary Codebook Generation (Cont.) Temporary Codebook Temporary Codebook G2 = { g2,1={84, 170, 166, 167, 84, …, 170}, g2,2={86, 168, 165, 170, 90, …, 165}, g2,3={84, 170, 166, 167, 83, …, 168}} Gn+1 = { gn+1,1={220, 212, 182, 179, 240, …, 246}} G2 = { g2,1={84, 170, 166, 167, 84, …, 170}, g2,2={86, 168, 165, 170, 90, …, 165}, g2,3={84, 170, 166, 167, 83, …, 168}} G1 = { g1,1={199, 96, 84, 167, 83, …, 130}, g1,2={201, 97, 90, 167, 85, …, 132}, g1,3={200, 95, 82, 167, 81, …, 131}} G1 = { g1,1={199, 96, 84, 167, 83, …, 130}, g1,2={201, 97, 90, 167, 85, …, 132}, g1,3={200, 95, 82, 167, 81, …, 131}} G3 = { g3,1={184, 83, 194, 170, 166, …, 110}, g3,2={180, 80, 194, 166, 168, …, 114}, g3,3={185, 85, 190, 172, 160, …, 120}, g3,4={191, 88, 197, 170, 162, …, 107}} G3 = { g3,1={184, 83, 194, 170, 166, …, 110}, g3,2={180, 80, 194, 166, 168, …, 114}, g3,3={185, 85, 190, 172, 160, …, 120}, g3,4={191, 88, 197, 170, 162, …, 107}} Gn = { gn,1={244, 83, 174, 210, 166, …, 127}, gn,2={243, 80, 175, 213, 168, …, 128}, gn,3={240, 85, 176, 209, 160, …, 126}, gn,4={244, 88, 178, 213, 162, …, 127}} Gn = { gn,1={244, 83, 174, 210, 166, …, 127}, gn,2={243, 80, 175, 213, 168, …, 128}, gn,3={240, 85, 176, 209, 160, …, 126}, gn,4={244, 88, 178, 213, 162, …, 127}} Gn+1 = { gn+1,1={220, 212, 182, 179, 240, …, 246}}
Codebook Refining IF ||Gi|| > THF = 3 Then Add Gi into Frequently-used part Else add Gi into Infrequently-used part Temporary Codebook ||Gn+1|| =1 Gn+1 = { gn+1,1={220, 212, 182, 179, 240, …, 246}} G2 = { g2,1={84, 170, 166, 167, 84, …, 170}, g2,2={86, 168, 165, 170, 90, …, 165}, g2,3={84, 170, 166, 167, 83, …, 168}} Frequently-used ||G2|| =3 Gn G1 = { g1,1={199, 96, 84, 167, 83, …, 130}, g1,2={201, 97, 90, 167, 85, …, 132}, g1,3={200, 95, 82, 167, 81, …, 131}} ||G1|| =3 G3 G3 = { g3,1={184, 83, 194, 170, 166, …, 110}, g3,2={180, 80, 194, 166, 168, …, 114}, g3,3={185, 85, 190, 172, 160, …, 120}, g3,4={191, 88, 197, 170, 162, …, 107}} ||G3|| =4 Infrequently-used Gn+1 G2 Gn = { gn,1={244, 83, 174, 210, 166, …, 127}, gn,2={243, 80, 175, 213, 168, …, 128}, gn,3={240, 85, 176, 209, 160, …, 126}, gn,4={244, 88, 178, 213, 162, …, 127}} ||Gn|| =4 G1
Codebook Refining (Cont.) For frequently-used part c3={185, 84, 194, 170, 164, …, 113} Compute Gi’s centroid cn={243, 85, 176, 211, 164, …, 127} G3 = { g3,1={84, 83, 94, 170, 166, …, 210}, g3,2={80, 80, 94, 166, 168, …, 214}, g3,3={85, 85, 90, 172, 160, …, 220}, g3,4={91, 88, 97, 170, 162, …, 207}} : ∵d(c3, cn) = 32 THH = 35 ∴ Combine c3 and cn by c3’ = (c3 + cn)/2 Use the centroids to represent the codewords c3={185, 84, 194, 170, 164, …, 113} Gn = { gn,1={244, 83, 174, 210, 166, …, 127}, gn,2={243, 80, 175, 213, 168, …, 128}, gn,3={240, 85, 176, 209, 160, …, 126}, gn,4={244, 88, 178, 213, 162, …, 127}} cn={243, 85, 176, 211, 164, …, 127} c3’={214, 85, 185, 191, 164, …, 120} : Centroid of Gn
Codebook Refining (Cont.) For infrequently-used part c1={200, 96, 85, 167, 83, …, 131} c2={85, 170, 166, 169, 86, …, 168} Compute Gi’s centroid cn+1={220, 212, 182, 179, 240, …, 246} Gn+1 = {gn+1,1={220, 212, 182, 179, 240, …, 246}} cn+1={220, 212, 182, 179, 240, …, 246} Use the centroids to represent the codewords G2 = {g2,1={84, 170, 166, 167, 84, …, 170}, g2,2={86, 168, 165, 170, 90, …, 165}, g2,3={84, 170, 166, 167, 83, …, 168}} c2={85, 170, 166, 169, 86, …, 168} G1 = { g1,1={199, 96, 84, 167, 83, …, 130}, g1,2={201, 97, 90, 167, 85, …, 132}, g1,3={200, 95, 82, 167, 81, …, 131}} c1={200, 966, 85, 167, 83, …, 131}
Codebook Refining (Cont.) Frequently-used part C3’={214, 85, 185, 191, 164, …, 120} : ∵d(c3’, c1) = 132.57 THL = 135 ∴ Delete c1 from Infrequently-used part Infrequently-used part c1={200, 96, 85, 167, 83, …, 131} c1={200, 96, 85, 167, 83, …, 131} c2={85, 170, 166, 169, 86, …, 168} c2={85, 170, 166, 169, 86, …, 168} cn+1={220, 212, 182, 179, 240, …, 246} cn+1={220, 212, 182, 179, 240, …, 246}
Codebook Refining (Cont.) Frequently-used part C3’={214, 85, 185, 191, 164, …, 120} C3’={214, 85, 185, 191, 164, …, 120} c2={85, 170, 166, 169, 86, …, 168} : : Infrequently-used part c2={85, 170, 166, 169, 86, …, 168} ∵ No any codeword cj from frequently-used part satisfies d(c2, cj) THL = 135 ∴ Add c2 into frequently-used part and delete c2 from infrequently-used part cn+1={220, 212, 182, 179, 240, …, 246}
Codebook Refining (Cont.) Frequently-used part C3’={214, 85, 185, 191, 164, …, 120} C3’={214, 85, 185, 191, 164, …, 120} c2={85, 170, 166, 169, 86, …, 168} c2={85, 170, 166, 169, 86, …, 168} cn+1={220, 212, 182, 179, 240, …, 246} : : Generated codebook Infrequently-used part cn+1={220, 212, 182, 179, 240, …, 246} ∵ No any codeword cj from frequently-used part satisfies d(cn+1, cj) THL = 135 ∴ Add cn+1 into frequently-used part and delete cn+1 from infrequently-used part Empty
Image Compression Generated codebook w 1 h C0={214, 85, 185, 191, 164, …, 120} c1={85, 170, 166, 169, 86, …, 168} : cn={220, 212, 182, 179, 240, …, 246} Index table Image
Experimental Results (b) Goldhill (a) Alan (c) Lena (d) Tiffany
Experimental Results (Cont.) (a) Codebook size comparison
Experimental Results (Cont.) (b) PSNR comparison with different THs
Conclusions • The proposed method significantly reduces the size of codebook and maintains a good image quality of the compressed images.