Block Truncation Coding Chapter 9 2022212 1 MomentPreserving

Block Truncation Coding Chapter 9 2022/2/12 資料壓縮 ※ 第九章 方塊截短編碼 ※ 1

Moment-Preserving Quantizer 2022/2/12 資料壓縮 ※ 第九章 方塊截短編碼 ※ 4

Moment-Preserving Quantizer 2022/2/12 資料壓縮 ※ 第九章 方塊截短編碼 ※ 5

Moment-Preserving Quantizer n Difficulties for hardware implementation : n square function n square root function 2022/2/12 資料壓縮 ※ 第九章 方塊截短編碼 ※ 6

Absolute Moment BTC (AMBTC) n Designed to preserve the absolute value of the moment. no absolute fn is needed !!! 2022/2/12 資料壓縮 ※ 第九章 方塊截短編碼 ※ 7

Absolute Moment BTC (AMBTC) n AMBTC has better MSE (i. e. , smaller) or equal MSE, compared with conventional BTC. 2022/2/12 資料壓縮 ※ 第九章 方塊截短編碼 ※ 8

Coding of the Bit Map and Reconstruction Levels n n Accurate mean value is not so significant at high activity ( ) regions. However, it is significant at low activity regions. Vector quantization of the reconstruction levels n n Consider ( , ) or ( , ), instead of (a, b), as a vector. Bit map omission n n 2022/2/12 If is very small, then a b. So, bit map can be ignored. 資料壓縮 ※ 第九章 方塊截短編碼 ※ 9

Coding of the Bit Map and Reconstruction Levels n Joint quantization of the reconstruction levels : ( , ) or ( , ) 6 bits suffice for ( , ) 2022/2/12 資料壓縮 ※ 第九章 方塊截短編碼 ※ 10

BTC Properties n n n Little computation Simplementation Moderate reconstruction quality Bit Rate Limitation Fixed partition failing to exploit local characteristic 2022/2/12 資料壓縮 ※ 第九章 方塊截短編碼 ※ 11

Adaptive AMBTC n Mode A : If | a-b | T 1; a low-activity region is detected and 4 4 blocks are used. Only one 8 -bit average value is transmitted (no bit-map). n Mode B : If Moderate activity and lack of large steps are detected and 4 4 blocks are used. Two 8 -bit reconstruction values plus a 16 -bit bit-map is transmitted. 2022/2/12 資料壓縮 ※ 第九章 方塊截短編碼 ※ 12

Adaptive AMBTC n n Mode C : In all other cases a 2 2 block size is used and two 8 -bit reconstruction values plus a 4 bit bit-map for each 2 2 block is transmitted. Probabilities for each class : n n T 1=1, T 2=20, T 3=60 Lenna n n Boots n 2022/2/12 (0. 004, 0. 740, 0. 256) (0. 015, 0. 495, 0. 526) 資料壓縮 ※ 第九章 方塊截短編碼 ※ 13

n AMBTC at 2. 0 bpp 2022/2/12 Results 資料壓縮 ※ 第九章 方塊截短編碼 ※ 15

Results n Adaptive AMBTC at 2. 89 bpp 2022/2/12 資料壓縮 ※ 第九章 方塊截短編碼 ※ 16

Results n AMBTC at 2. 0 bpp 2022/2/12 資料壓縮 ※ 第九章 方塊截短編碼 ※ 17

Conclusions n Refer to the exercises for more discussions about color images coding by AMBTC and AMBTC by quadtree. 2022/2/12 資料壓縮 ※ 第九章 方塊截短編碼 ※ 18