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- Block Truncation Coding (BTC) is a type of lossy image compression technique for greyscale images. It divides the original images into blocks and then uses a quantizer to reduce the number of grey levels in each block whilst maintaining the same mean and standard deviation. It is an early predecessor of the popular hardware DXTC technique, although BTC compression method was first adapted to color long before DXTC using a very similar approach called Color Cell Compression. BTC has also been adapted to video compression. BTC was first proposed by Professors Mitchell and Delp at Purdue University. Another variation of BTC is Absolute Moment Block Truncation Coding or AMBTC, in which instead of using the standard deviation the first absolute moment is preserved along with the mean. AMBTC is computationally simpler than BTC and also typically results in a lower Mean Squared Error (MSE). AMBTC was proposed by Maximo Lema and Robert Mitchell. Using sub-blocks of 4×4 pixels gives a compression ratio of 4:1 assuming 8-bit integer values are used during transmission or storage. Larger blocks allow greater compression ("a" and "b" values spread over more pixels) however quality also reduces with the increase in block size due to the nature of the algorithm. The BTC algorithm was used for compressing Mars Pathfinder's rover images. (en)
- 方块编码（英語：Block Truncation Coding，縮寫：BTC）是一种用于灰度图像的有损数据压缩算法。这种算法将图像分为以方块为单位，在每一方块中，在保持原有平均数和标准方差（即保持二阶矩）的同时，减少灰度等级，以达到压缩的目的。方块编码被认为是纹理压缩算法的前身；但在DXTC出现之前很久，方块编码已就被引入彩色图像的压缩，即色彩单元压缩。 方块编码也被采用于視訊壓縮 中。 方块编码由普渡大學的米歇尔和德尔普两位教授首先提出。如果以4x4的方块为基本单位，用8比特的整型来传输或存储，这种算法可以达到4：1的压缩比率。如果用更大尺寸的方块，可以达到更大的压缩比率，但图像质量也会相应地降低。 这种算法也被用于了火星探路者的图像压缩。 (zh)
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- 方块编码（英語：Block Truncation Coding，縮寫：BTC）是一种用于灰度图像的有损数据压缩算法。这种算法将图像分为以方块为单位，在每一方块中，在保持原有平均数和标准方差（即保持二阶矩）的同时，减少灰度等级，以达到压缩的目的。方块编码被认为是纹理压缩算法的前身；但在DXTC出现之前很久，方块编码已就被引入彩色图像的压缩，即色彩单元压缩。 方块编码也被采用于視訊壓縮 中。 方块编码由普渡大學的米歇尔和德尔普两位教授首先提出。如果以4x4的方块为基本单位，用8比特的整型来传输或存储，这种算法可以达到4：1的压缩比率。如果用更大尺寸的方块，可以达到更大的压缩比率，但图像质量也会相应地降低。 这种算法也被用于了火星探路者的图像压缩。 (zh)
- Block Truncation Coding (BTC) is a type of lossy image compression technique for greyscale images. It divides the original images into blocks and then uses a quantizer to reduce the number of grey levels in each block whilst maintaining the same mean and standard deviation. It is an early predecessor of the popular hardware DXTC technique, although BTC compression method was first adapted to color long before DXTC using a very similar approach called Color Cell Compression. BTC has also been adapted to video compression. (en)
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- Block Truncation Coding (en)
- 方块编码 (zh)
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