Anaglyph Generator. Computer Science Department University of Bologna, Italy Francesconi Alessandro, Limone Gian Piero December 2011

Transcription

1 Anaglyph Generator Computer Science Department University of Italy Francesconi Alessandro, Limone Gian Piero December 2011

2 2 1 ofitaly What is AG? The Anaglyph Generator (AG) program allows to generate a 3D anaglyph image from a classic 2D one.

3 3 2 ofitaly What is an Anaglyph? An anaglyph is an image made up of two color layers, tipically red and cyan, that, observed by the use of a particular type of glasses, shows depth properties of the image giving the idea of 3D. The picture contains two differently filtered colored images, one for each eye. When viewed through the color coded "anaglyph glasses", they reveal an integrated stereoscopic image. The visual cortex of the brain fuses this into perception of a 3D scene or composition.

4 4 3 ofitaly Depth Information A 3D image allows to the observer to better identify objects composing the scene and their position in it providing depth information. To have these information in Computer Graphic, one of the possibilities is to join the original image with the related depth map, a gray scale image: objects placed closer to the observer are depicted in white color, while, as the objects move away to the background, they are darker depicted.

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6 6 4 ofitaly How to Create an Anaglyph (1/3) To create an anaglyph it is necessary have got: a) the original 2D image provides the original image to convert; b) the related depth map gives depth information; c) the shift_value suggests how many pixels the image should be shifted. The program consists of 3 phases: 1) Depth Map Study consider the depth map as a set of depth levels; at depths greater match levels which pixels tend to 0 value (black pixels) while to closer levels match pixels with 1 tending values (white pixels). To simulate the nearness or distance of the scene's objects from the observer each pixel of the original image must be translated on the X-axis by an offset value depends on shift_value; for each depth map's (x,y) pixel, very dark values will corresponds a tranlation to a side of the original image, brighter will corresponds translation to the other side, while, pixels whose values are around 0.5 will undergo minor changes. 2) Red and Cyan Images Construction applying to the original image right and left side shift we will get 2 matrices that, respectively, are then multiplied by 2 other matrices, first one rappresenting red color, second one cyan. 3) Merge merging these 2 copies the final anaglyph is provided.

7 5 ofitaly How to Create an Anaglyph (2/3) 7

8 8 6 ofitaly How to Create an Anaglyph (3/3)

9 9 7 ofitaly Depth Map Retrieval (1/3) The Algorithm used by AG to infer a depth map from the original image only is based on the A Novel 2D-to-3D Conversion System Using Edge Information (C.Cheng, C.Li, L.Chen) article. To obtain the depth map: 1) Image Segmentation inside the original image are identified N color regions, based on the percentage of colors within it; 2) for each pixel of every region is assigned an integer identifier number, from 1 to N; 3) to each region is applied the following formula:

10 10 8 ofitaly Depth Map Retrieval (2/3) Depth Map gradients orientation: a) left Þ Wrl= 0, Wud= -1; b) left-down Þ Wrl= 0.5, Wud= -0.5; c) down Þ Wrl= 1, Wud= 0 (Default Choice); d) right-down Þ Wrl= -0.5, Wud= -0.5; e) right Þ Wrl= 0, Wud= 1.

11 9 ofitaly Depth Map Retrieval (3/3) Þ Blocks= 3 (Default value) 11

12 12 Slide 10 ofitaly 15- Francesconi Alessandro, Limone Gian Piero Anaglyph Generator - University of Let's see AG in action...

13 13 Slide 11 ofitaly 15- Francesconi Alessandro, Limone Gian Piero Anaglyph Generator - University of OBSERVATIONS A) ImageCapture" function does not work on Unix; B) Image processor programs as Photoshop and Gimp allow to manage the scaling operation by 3 functions, WRAP, SMEAR and BLACK; AG provides it but without loosing image informations in the interessed image area; C) The AG program turns out to be a bit slow: Intel Pentium Dual CPU 2.00 GHz ; Depth Map Generation 640x480 image Blocks= sec ; Anaglyph Generation 640x480 image sec. The end result has been obtained without the use of FOR loops in the computation of matrices but using "Table" construct and replacing the use of "ImageValue" with "ImageData" (during pixel information extraction); D) The algorithm to create automatically the depth map does not work efficiently on all images...

14 14 Slide 12 ofitaly 15- Francesconi Alessandro, Limone Gian Piero Anaglyph Generator - University of Conclusions and Further Works We note it is difficult obtain a depth map from a single image and withot additional information; the algorithm used by AG is good enough to do that but extremely optimizable. 1) optimization of depth map retrieval algorithm; 2) implementation of new depth map retrieval algorithms; 3) optimization of computation timing; 4) implementation of additional anaglyph color schemes.

15 15 Slide 13 ofitaly 15- Francesconi Alessandro, Limone Gian Piero Anaglyph Generator - University of References A Novel 2D-to-3D Conversion System Using Edge Information, Chao-Chung Cheng, Chung-Te Li, Liang-Gee Chen, IEEE; ; GIMP "Displace" function's source code, ; Possible future working readings: Depth Estimation using Monocular and Stereo Cues, A. Saxena, J. Schulte and A. Y. Ng, Stanford University CA; Depth-Map Generation by Image Classification, S. Battiato, S. Curti, M. La Cascia, M. Tortora, E. Scordato, STMicroelectronics- AST Catania LAB, University of Palermo.

16 16 Slide 14 ofitaly 15- Francesconi Alessandro, Limone Gian Piero Anaglyph Generator - University of

17 Slide 15 ofitaly 15- Francesconi Alessandro, Limone Gian Piero Anaglyph Generator - University of Any Question? 17