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dct

于 2010-05-29 发布 文件大小:1491KB
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   在一个图像块中调整两个(或多个) DCT系数的相对大小。将描述一个使用数字图像作为载体的系统。在编码处理中,发送者将载体图像分成8×8的像素块,每一块只精确地编码一个秘密信息位。嵌入过程开始时,首先伪随机地选择一个图像块bi,用它对第i个消息比特进行编码。令Bi=D{bi}为DCT变换后的图像块。 在通信开始前,发送者和接收者必须对嵌入过程中使用的两个DCT系数的位置达成一致,让我们用(u1,v1)和(u2,v2)来表示这两个索引。这两个系数应该相应于余弦变换的中频,确保信息保存在信号的重要部位(从而使嵌入信息不容易因JPEG压缩而完全丢失 (abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwx)

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