Simulating short depth of field to maximize privacy in videotelephony
An arrangement for simulating a short depth of field in a captured videophone image is provided in which the background portion of the image is digitally segregated and blurred to render it indistinct. Thus, the displayed video of a user in the foreground is kept in focus while the background appears to be out of focus. Image tracking or fixed templates are used to segregate an area of interest that is kept in focus from the remaining captured video image. Image processing techniques are applied to groups of pixels in the remaining portion to blur that portion of the captured video image. Such techniques include the application of a filter that are alternatively selected from convolution filters in the spatial domain (e.g., mean, median, or Gaussian filters), or frequency filters in the frequency domain (e.g., low-pass or Gaussian filters). User-selectable control is optionally implemented for controlling the type of foreground/background segregation technique utilized (i.e., dynamic face-tracking or fixed template shape), degree of blurring applied to the background, and on/off control of the background blurring.
1. A videophone, comprising:
a camera arranged for capturing a video image comprising a plurality of pixels; and
an image processing module arranged for applying privacy filtering to the video image to simulate a depth of field effect, the privacy filtering including
(a) segregating a portion of the video image, and (b) blurring the segregated portion of the video image by increasing the circle of confusion associated with the segregated portion of the video image.
2. The videophone of claim 1 in which the image processing module blurs the segregated portion of the video image using one of mean filter, median filter, or Gaussian filter that is applied to pixels in the segregated portion of the video image in a spatial domain.
3. The videophone of claim 1 in which the image processing module blurs the segregated portion of the video image using one of low pass filter or Gaussian filter that is applied to pixels in the segregated portion in order to increase the circle of confusion associated with the segregated portion of the video image in a frequency domain.
4. The video phone of claim 1 in which the blurred portion of the video image is combined with at least a portion of an unblurred portion of the video image to generate a composite video image.
5. The videophone of claim 1 in which the image processing module is implemented in one of software application, firmware, hardware, or a combination thereof.
6. The videophone of claim 1 in which the size or shape of the segregated portion of the video image that is blurred is selected from one or more templates.
7. The videophone of claim 1 further including a user interface arranged for selectable control over the privacy filtering.
8. The videophone of claim 7 in which the user interface is arranged for enabling and disabling the privacy filtering.
9. The videophone of claim 7 in which the user interface is arranged for selecting an extent to which the segregated portion of the video image is blurred.
10. The videophone of claim 7 in which the user interface is arranged for selecting a size or shape of the segregated portion of the video image that is blurred.
11. A computer-readable medium containing instructions which, when executed in one or more processors disposed in an electronic device, performs a method for providing privacy to a videotelephony call, the method comprising the steps of:
capturing a video image with a videophone camera;
applying an object detection algorithm to segregate a target portion of the video image from a remaining portion of the video image;
digitally filtering the remaining portion of the video image by increasing the circle of confusion associated with the remaining portion to provide privacy for subject matter contained therein; and
compositing the target portion with the filtered remaining portion to generate a composite video image.
12. The computer-readable medium of claim 11 further including a step of transmitting the composite video image to a videophone on a remote end of the videotelephony call.
13. The computer-readable medium of claim 12 in which the transmitting is in a format that utilizes video compression, the format being selected from one of MPEG, MPEG-1, MPEG-2, MPEG-4, MPEG-7, MPEG-21, VC-1, DV, DivX, ITU H.261, TTU H.263, ITU H.264, WMV, Real Media, Real Video, QuickTime, ASF, AVI, 3GPP, 3GPP2, JPEG, or motion-JPEG.
14. The computer-readable medium of claim 11 in which the digital filtering comprises applying a convolution operator in one of spatial domain or frequency domain.
15. The computer-readable medium of claim 11 in which the digital filtering comprises applying an image in place of the remaining portion of the video image, the image being selected from one of illustration, pattern, featureless image, colored image, photograph or illustration.
16. A method for simulating depth of field effects in a video image, the method comprising the steps of:
utilizing an image sensor to capture the video image having a substantially infinite depth of field;
spatially segregating a portion of the video image into an image buffer;
applying image processing to the segregated video portion to increase a circle of confusion associated with the segregated portion so as to shorten an apparent depth of field of the video image; and
refreshing the image buffer with the image-processed video portion.
17. The method of claim 16 in which the spatial segregation is performed using an object detection technique to dynamically locate and track a portion of interest in the video image.
18. The method of claim 17 in which the object detection technique is selected from one of feature-based approach or image-based approach.
19. The method of claim 16 in which the image sensor is a CCD array that is small relative to an associated image sensor lens aperture.
20. The method of claim 19 in which the lens is arranged to provide a fixed focal length.