Showing papers on "Image gradient published in 2002"

Segmentation and histogram generation using the HSV color space for image retrieval

Abstract: We have analyzed the properties of the HSV (hue, saturation and value) color space with emphasis on the visual perception of the variation in hue, saturation and intensity values of an image pixel. We extract pixel features by either choosing the hue or the intensity as the dominant property based on the saturation value of a pixel. The feature extraction method has been applied for both image segmentation as well as histogram generation applications - two distinct approaches to content based image retrieval (CBIR). Segmentation using this method shows better identification of objects in an image. The histogram retains a uniform color transition that enables us to do a window-based smoothing during retrieval. The results have been compared with those generated using the RGB color space.

Using Prior Shapes in Geometric Active Contours in a Variational Framework

Abstract: In this paper, we report an active contour algorithm that is capable of using prior shapes. The energy functional of the contour is modified so that the energy depends on the image gradient as well as the prior shape. The model provides the segmentation and the transformation that maps the segmented contour to the prior shape. The active contour is able to find boundaries that are similar in shape to the prior, even when the entire boundary is not visible in the image (i.e., when the boundary has gaps). A level set formulation of the active contour is presented. The existence of the solution to the energy minimization is also established. We also report experimental results of the use of this contour on 2d synthetic images, ultrasound images and fMRI images. Classical active contours cannot be used in many of these images.

A classified and comparative study of edge detection algorithms

Abstract: Since edge detection is in the forefront of image processing for object detection, it is crucial to have a good understanding of edge detection algorithms. This paper introduces a new classification of most important and commonly used edge detection algorithms, namely ISEF, Canny, Marr-Hildreth, Sobel, Kirsch, Lapla1 and Lapla2. Five categories are included in our classification, and then advantages and disadvantages of some available algorithms within this category are discussed. A representative group containing the above seven algorithms are the implemented in C++ and compared subjectively, using 30 images out of 100 images. Two sets of images resulting from the application of those algorithms are then presented. It is shown that under noisy conditions, ISEF, Canny, Marr-Hildreth, Kirsch, Sobel, Lapla2, Lapla1 exhibit better performance, respectively.

Method of extracting image from input image using reference image

Abstract: This invention relates to an image processing method for precisely and automatically recognizing a specific image extraction region to be divided from an input image, and extracting the specific image extraction region. Thresholding is done for intensity differences of edge data obtained from the input data to extract difference edge data. A main extraction region is estimated from the outermost contour line extracted based on the extraction result of the difference edge data. Thresholding or the like is done in units of pixels of the input image to extract an initial region. Extraction region determination processing is done for extracting an accurate target region by combining the main extraction region and initial region.

Robust full-motion recovery of head by dynamic templates and re-registration techniques

Abstract: This paper presents a method to recover the full-motion (3 rotations and 3 translations) of the head using a cylindrical model. The robustness of the approach is achieved by a combination of three techniques. First, we use the iteratively re-weighted least squares (IRLS) technique in conjunction with the image gradient to deal with non-rigid motion and occlusion. Second, while tracking, the templates are dynamically updated to diminish the effects of self-occlusion and gradual lighting changes and keep tracking the head when most of the face is not visible. Third, because the dynamic templates may cause error accumulation, we re-register images to a reference frame when head pose is close to a reference pose. The performance of the real-time tracking program was evaluated in three separate experiments using image sequences (both synthetic and real) for which ground truth head motion is known. The real sequences included pitch and yaw of as large as 40/spl deg/ and 75/spl deg/ respectively. The average recovery accuracy of the 3D rotations was found to be about 3/spl deg/.

Smoothing low-SNR molecular images via anisotropic median-diffusion

Abstract: We propose a new anisotropic diffusion filter for denoising low-signal-to-noise molecular images. This filter, which incorporates a median filter into the diffusion steps, is called an anisotropic median-diffusion filter. This hybrid filter achieved much better noise suppression with minimum edge blurring compared with the original anisotropic diffusion filter when it was tested on an image created based on a molecular image model. The universal quality index, proposed in this paper to measure the effectiveness of denoising, suggests that the anisotropic median-diffusion filter can retain adherence to the original image intensities and contrasts better than other filters. In addition, the performance of the filter is less sensitive to the selection of the image gradient threshold during diffusion, thus making automatic image denoising easier than with the original anisotropic diffusion filter. The anisotropic median-diffusion filter also achieved good denoising results on a piecewise-smooth natural image and real Raman molecular images.

A method and system for selectively applying enhancement to an image

Abstract: A method for processing a digital color image includes the steps of: providing a subject matter detector for distinguishing between target and background subject matters; applying the subject matter detector to the image to produce a belief map indicating the degree of belief that pixels in the image belong to target subject matter; providing an image enhancement operation that is responsive to a control signal for controlling the degree of image enhancement; and applying image enhancement to the digital image by varying the control signal according to the belief map to produce an enhanced image.

Geometry and Color in Natural Images

Abstract: Most image analysis algorithms are defined for the grey level channel, particularly when geometric information is looked for in the digital image. We propose an experimental procedure in order to decide whether this attitude is sound or not. We test the hypothesis that the essential geometric contents of an image is contained in its level lines. The set of all level lines, or topographic map, is a complete contrast invariant image description: it yields a line structure by far more complete than any edge description, since we can fully reconstruct the image from it, up to a local contrast change. We then design an algorithm constraining the color channels of a given image to have the same geometry (i.e. the same level lines) as the grey level. If the assumption that the essential geometrical information is contained in the grey level is sound, then this algorithm should not alter the colors of the image or its visual aspect. We display several experiments confirming this hypothesis. Conversely, we also show the effect of imposing the color of an image to the topographic map of another one: it results, in a striking way, in the dominance of grey level and the fading of a color deprived of its geometry. We finally give a mathematical proof that the algorithmic procedure is intrinsic, i.e. does not depend asymptotically upon the quantization mesh used for the topographic map. We also prove its contrast invariance.

Local digital image property control with masks

Abstract: Disclosed is a process for the location dependent correction of photographic image data representing an image with a multitude of image elements, whereby the image data determine color values and at least one image property for the image elements, including the steps of: determining a correction mask with a multitude of correction elements based on the photographic image data to be corrected, whereby the correction elements are assigned to the image data and determine correction changes for the image data corresponding to the image element, the correction changes corresponding to changes of the at least one image property; and applying the correction mask to the image data, whereby the image data are changed corresponding to the correction elements.

New improvements to range image segmentation by edge detection

Abstract: This article presents new improvements to range image segmentation based on edge detection techniques The developed approach better preserves the object's topology and shape even to noisy images The algorithm also does not depend on rigid threshold values, thus being useful in unsupervised systems Experiments were performed in a popular range image database and the results were compared to four other traditional range image segmentation algorithms, demonstrating the efficiency of the proposed algorithm

Image signal coding method, image signal coding apparatus and storage medium

Abstract: Provided are a depth image obtaining section that obtains a depth image from the same viewpoint as in the input image, a layer section that separates the input image into a foreground image and a background image as layered images using depth information of the depth image, a coding section that encodes the foreground image, a background sprite generating section that generates a background sprite image from the background image, and a sprite coding section that encodes the background sprite image. The depth image from the same viewpoint as in the input image is obtained in the depth image obtaining section, the input image is separated into a foreground image and a background image as layered images using the depth information, and based on the separated background image, a background sprite image is generated.

Method for locating faces in digital color images

Abstract: A digital image processing method for locating faces in a digital color image includes the steps of: generating a mean grid pattern element (MGPe) image from a plurality of sample face images; generating an integral image from the digital color image; and locating faces in the color digital image by using the integral image to perform a correlation between the mean grid pattern element (MGPe) image and the digital color image at a plurality of effective resolutions by reducing the digital color image to grid pattern element images (GPes) at different effective resolutions and correlating the MGPe with the GPes.

Method and apparatus for image enhancement for the visually impaired

Abstract: A method and apparatus providing good image enhancement for the visually impaired utilizing the “Ullman-Zur enhancement” algorithm. The method and apparatus consists in obtaining an original image, detecting and enhancing the edges and lines of the image by using Balanced Difference of Gaussians to obtain a first processed image, smoothing the original image by using a convolution of the original image with Gaussian, enhancing the contrast of the smoothed image, calculating the intensity average, AC, and the standard deviation of the intensity, SDC, of the chosen region, and stretching the intensity of the smoothed image linearly according to AC, SDC, and some specific rules to obtain a second processed enhanced image. The first processed image is superimposed on the second processed enhanced image to obtain the final enhanced image that is more readily perceived by a visually impaired person.

Adaptive demosaicing with the principal vector method

Abstract: Demosaicing is the process of interpolating the missing colors in an image that is acquired from a digital image sensor equipped with a color filter array. This paper describes a spatially adaptive demosaicing algorithm that is based on the Jacobian matrix of the color map and neighborhood voting. The algorithm requires only additions, subtractions and shifts, and is therefore attractive from a computational point of view. Comparisons are provided to show that the algorithm improves on published algorithms in terms of complexity or image quality.

Canny edge based image expansion

Abstract: In this paper, a Canny edge-based image expansion method is introduced. Our proposed expansion method outperforms the pixel replication, the bilinear interpolation and the bicubic interpolation methods. It gives crisp and less zigzag pictures. Our method is applied on the image after it has been expanded using bilinear or bicubic interpolation. The edges of such an expanded image are obtained using the Canny edge detector. The values of pixels around the edges are modified to yield a crisper and less zigzagged picture.

Edge detection based on background change

Abstract: A method detects edges of an object in a scene by first acquiring a static image of the scene when the scene is static, and a live image of the scene including the object A reference image is constructed from the static image Then, image gradients of the reference image are compared with image gradients of the live image to identify edges of the object in the live image

Digital image compression

Abstract: A method of reconstructing an image, where the input image data is preferably part I or part II compliant JPEG2000 coded data, or pixel data of the original image. The method selects ( 810 ) an output resolution R, and then determines a number of sub-passes to extract from each block code based on the selected resolution. The method then extracts ( 830 ) the determined sub-passes and the remaining sub-passes are discarded. The method then reconstructs 840 the image from the extracted sub-passes. The reconstructed image can be in the form of the selected resolution of the original image, or it can be in the form of compressed image data of the selected resolution of the original image.

An effective content-based visual image retrieval system

Abstract: An effective content-based visual image retrieval system is presented. This system consists of two main components: visual content extraction and indexing, and query engine. Each image in the image database is represented by its visual features: color and spatial information. The system uses a color label histogram with only thirteen bins to extract the color information from an image in the image database. A unique unsupervised segmentation algorithm combined with the wavelet technique generates the spatial feature of an image automatically. The resulting feature vectors are relatively low in dimensions compared to those in other systems. The query engine employs a color filter and a spatial filter to dramatically reduce the search range. As a result, queue processing is speeded up. The experimental results demonstrate that our system is capable of retrieving images that belong to the same category.

Interpolated image filtering method and apparatus

Abstract: A technique for processing a digital image in which an operator selection of a field of view triggers the automatic selection of a shrink factor, so that image processing and quality is uniform regardless of the operator selection. Processing of the image includes shrinking the image by the shrink factor, identifying structural elements within the image, differentially processing the structure and non-structure elements, expanding the image by the shrink factor, and texture blending the processed image with the original image. Optionally, high frequency noise may also be blended with the processed image to improve perceived image quality.

Image segmentation using gradient vector diffusion and region merging

Abstract: The Active Contour (or Snake) Model is recognized as one of the efficient tools for 2D/3D image segmentation. However traditional snake models prove to be limited in several aspects. The present paper describes a set of diffusion equations applied to image gradient vectors, yielding a vector field over the image domain. The obtained vector field provides the Snake Model with an external force as well as an automatic way to generate the initial contours. Finally a region merging technique is employed to further improve the segmentation results.

System with motion triggered processing

Abstract: A document image capture (scanning) system and control method are described for scanning and processing document images received live from a camera. A motion detector detects image motion between two image frames. When the image is stationary, image processing (such as OCR) is carried out automatically and made available to the operator. In one form, when movement is detected, the image processing results are discarded until the image is newly stationary, whereupon new image processing is carried out on the new image. In another form, the degree of movement is evaluated; if the movement is small, then at least some of the previous image processing results are re-used by re-mapping on to the new image.

Image processing method, image processing apparatus and image processing program

Abstract: An image processing method includes the steps of obtaining an image in which a first area including a first image and a second area including a second image are discriminated with each other, and a control step for performing a blur control to a second image using a filter to obtain a blur-controlled second image while accompanying processing for reducing an influence of the first area at a boundary between the first area and the second area and therearound when the blur control is performed to the second image.

Local change of an image sharpness of photographic images with masks

Abstract: A process for the image sharpening of a photographic image with a multitude of image elements is disclosed, wherein a correction mask for the change of the image sharpness is determined from the image data representing the image to be corrected, whereby the elements of the correction mask for the change of the image sharpness locally describe the degree of contrast change to be carried out for the individual image elements, and whereby additional information relating to the image is used for the determination of the elements in addition to information on the local contrast.

Method and apparatus for automated image correction for digital image acquisition

Abstract: A method and apparatus for automatically correcting colors in digital image space comprises taking an image file of the object using a digital device, such as a digital camera or scanner. Profiling software checks compares the image file to a photograph of a target test sheet under specific lighting conditions, and checks the submitted object file for orientation, alignment, color intensity, and hue with respect to the target test sheet. A transformation image algorithm matches colors of the submitted image file with colors of the target test sheet and thereby creates a color corrected image profile for the submitted image file.

Highlight substitution in light fields

Abstract: Highlights occur especially when recording medical (color) images during micro-invasive operations. They disturb the physicians who can sometimes only guess the tissue at the position of the highlights. We present a new technique of highlight removal. A so-called light field is generated from the recorded image sequence. Then a binary highlight mask is computed for each image and used as confidence map for the light field pixels. The result is a light field in which pixels at highlight positions are interpolated by pixels which were not over-imposed by highlights. This leads to light fields with better images. We demonstrate and evaluate the technique on medical and synthetic image sequences.

Image processing apparatus and method, control program, and storage medium

Abstract: This invention has as its object to provide an image processing method which generates an image with a blur effect by an image process as if it were taken by a lens with a large aperture size, and can obtain a higher-resolution image. To this end, the method includes the input step of inputting a first image, and a second image which has parallax with respect to the first image, and the image processing step of executing different image processes for first, corresponding regions of the first and second images input in the input step, and second regions different from the first regions in these images, and compositing the first and second images.