線條化藝術畫之自動產生與其在資訊隱藏上之應用

Abstract

本論文研究探討了三種藝術影像的自動產生與資訊隱藏技術。這三種不同類型的藝術影像分別是「線條化類立體主義畫作」，「條狀化類未來主義畫作」，與「方塊化類新造型主義畫作」。除了建立一套自動產生這三種藝術畫的系統外，並利用其在影像處理上的特性，各提出了一種資訊隱藏的技術，以達到秘密傳輸之應用。第一種藝術畫─線條化類立體主義畫作的產生方式，是將一張原始影像用霍夫轉換方式找到影像中主要的線條，再用這些線條重新組合出立體單色形塊的新藝術。進而根據人類視覺對平均區塊顏色的敏感度較低這項特性，在維持區塊的顏色平均下，決定各個像素重新填色的方式，來達到藏入秘密訊息的效果。第二種藝術畫─條狀化類未來主義畫作的產生方式，是先將一張原始影像分割成許多單色大區塊，並依其方向特徵加以切割成條狀。另利用此藝術畫留白畫風的特性來產生不同填色的順序，達到藏入秘密訊息的效果。最後一種藝術畫─方塊化類新造型主義畫作的產生方式，是將一張原始影像用二元空間切割方式及相互信息(mutual information)進行遞迴式水平或垂直切割。本論文提出了兩個方法來利用此藝術畫來進行秘密傳輸：第一種是在二元空間分割過程中產生此影像的二元分割樹，利用微調葉節點的區塊平均色方式來達到藏入秘密訊息的效果；第二種是在區塊填色的時候，用二元空間切割方式逐步填色，用不同填色方向來達到藏入秘密訊息的效果。 除了上述的方法外，我們還提出了幾個增加安全性的方法，確保藏入的秘密資訊不被駭客發現。這些方法皆有實驗結果證明它們在視覺方面達到預期效果，以及在資訊隱藏技術上的可行性。

In this study, three kinds of line-type computer art images are created, called line-based Cubism-like image, strip-based Futurism-like image, and rectangle-based Neo-Plasticism-like image. Also proposed are three data hiding techniques for covert communication via these types of art images, respectively. In the creation of line-based Cubism-like images, the longer line segments in a source image are detected and rearranged to form a new 3D-like shape for each color component in the image. In a process of re-coloring the regions in the new image, a data hiding technique is designed skillfully to embed a secret message into the image by keeping the average color of the region unchanged. In the strip-based Futurism-like image creation process, the boundary chain codes of each region yielded by image segmentation are utilized to analyze the region characteristics such as corner points and region directions. By drawing the edges formed by the found corner points, an effect of polygon approximation of the prominent regions in the source image is obtained. Then, each region is partitioned into strips in accordance with the extracted region direction, and a given secret message is hidden into the resulting image by coloring the strips with the white color or the region’s average color in a random fashion. To generate a rectangle-based Neo-Plasticism-like image, a binary space-partition scheme is used to partition a given image into multiple rectangles with the maximum mutual information. Furthermore, two methods are proposed to hide a secret message into the generated art image. One is to limit the image partitioning directions (horizontal and vertical) to follow an alternative order and hide the secret messages into the leaf nodes of a partition tree yielded by the binary space-partition scheme. The other method does not limit the partitioning direction order, and fills the regions with horizontal or vertical color lines to embed the secret message. In addition, for each art image, the user is allowed to select some parameters to create his/her favorite art images. Various security enhancement measures are also proposed to make the embedded data more random to prevent hackers’ attacks. Experimental results showing the feasibility of the proposed methods for art image creation and data hiding applications are also included.