在影像中，嵌入多目的數位浮水印之目的是利用不同浮水印之特性以達多種之用途，較常見的是嵌入強健型及易碎型兩種特性之浮水印，以結合兩者的優點來達到保護與認證之目的。在網路媒體之傳輸上，有別於使用二值型浮水印(Binary Watermark)，近來對於灰階型浮水印(Grayscale Watermark)的使用有日漸普及之趨勢。
曾有學者在原始影像之區塊上利用奇異值分解(Singular Value Decomposition, SVD)所得之最大奇異值來嵌入灰階型浮水印，由於奇異值具有聚集影像大部分的能量及不受細微干擾而改變的特性，因此可利用修改能按大小排列之奇異值的最大值來嵌入灰階型浮水印，並且藉由深度因子(Depth Factor, DF)來調整浮水印的強健性，以避免對原始影像品質有過多影響。
為了加入竄改偵測能力之易碎型浮水印於此強健型灰階值浮水印之技術中，本論文修改利用區塊最大奇異值嵌入灰階型浮水印之方法，以縮小方法深度因子對原始影像的影響，然後再利用已嵌入灰階值浮水印之奇異值最低位元(Least Significant Bit, LSB)，產生一個二值型數列浮水印嵌入於影像區塊之最低位元，形成一易碎型浮水印以便偵測出影像受到竄改的區域，此形成一多目的灰階值浮水印技術。
由實驗證明本論文因此提出之方法，由於縮小深度因子對影像影響較以往學者所提之灰階型浮水印技術少，因此影像品質較佳，此外，在影像受到局部竄改或攻擊時能夠以影像區塊為單位偵測出受到竄改或攻擊之部分。在著作權保護方面，萃取浮水印的過程中亦不需要原始影像，只需要所有人的密鑰即可將此灰階型浮水印萃取出來，此外即使整個影像皆加入高斯雜訊或經過JPEG壓縮，亦可萃取出甚高品質之灰階值浮水印，以證明影像著作權之歸屬以達到著作權保護之功能。

The purpose of multipurpose digital watermarking technique is embedding different watermarks for combining their advantages such as fragile watermark and robust watermark. In network transmission, in order to protect and verify image; more and More digital watermark is adopted grayscale watermark different from binary watermark for protection and authentication in Internet Transmission。
The watermarking schemes based on the singular value decomposition (SVD) embed a watermark into singular values because these singular values have the most power of an image and can not be changed by small noise. By this property, the watermark embeds into the largest of singular value, avoiding having much effect for the quality of cover image.
For getting tamper detection ability in the robust grayscale watermarking scheme, first we modified the maximum of singular value in block and enhanced image quality by reducing depth factor(DF) effect. Then, we use conditions to determine how much modification in singular value, then. we can embed the binary bit string into the LSB of cover image, and use this watermark to detect which block of watermarked image is modified. We propose the multipurpose watermark scheme with verification and tamper detection ability.
By the experiment results, proposed scheme can defense normal attack and detect the modified regions with block unit. In the Copyright protection, proposed scheme can extract the high quality grayscale watermark only need keys without original cover image, and extracted watermark can overcome Gaussian noise attack and JPEG compression.

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