Patent ID: 7409104

Claim:
A method for enhancing wide dynamic range in images, the method comprising: acquiring at least two images of a scene to be imaged, the images acquired using different exposure times, wherein the acquired images are in JPEG format, the JPEG format including a DCT transform domain; constructing for a first image of said at least two images an illumination mask comprising a set of weight values distinctively identifying respective areas of pixels of high or low illumination, over-exposed or underexposed with respect to a predetermined threshold illumination value, assigning one of the weight values to each pixel, whereas other weight values are assigned to other pixels of the other of said at least two images; using a spatial low-pass filter to smooth border zones between pixels of one weight value and pixels of other weight values, thus assigning pixels in the border zones new weight values in a range between the weight values; and constructing a combined image in the DCT transform domain using image data of pixels assigned with one weight value of the first image and image data of pixels assigned with other weight values of the other of said at least two images and in pixels corresponding to the border zones using image data from said at least two images proportional to the new weight values, wherein the following relation is used in the constructing the combined image: I p,q DCT WDR =α( I DC Long ))* I p,q DCT Long +(1−α( I DC Long ))* I p,q DCT Short ·Ratio, where I DC Long is the DC coefficient of the DCT transform of the relatively longer exposure image, α is a weight representing the illumination mask, Ratio is a measure that defines the relationship between the images of different exposures, p, q are DCT coefficients, and*represents convolution.