JP2006041744A5

JP2006041744A5 -

Info

Publication number: JP2006041744A5
Application number: JP2004216417A
Authority: JP
Filing date: 2004-07-23
Publication date: 2007-10-04
Anticipated expiration: 2024-07-23

Claims

In an image processing apparatus for enhancing contrast of an original image composed of pixels having digitized density values,
Density shift means for shifting the density histogram of the original image on a predetermined density gradation;
Decomposition means for subjecting the image data of the original image subjected to the shift processing by the density shift means to multi-resolution decomposition to be decomposed into coefficient data including coefficients of a low frequency component and a high frequency component;
Weighting means for assigning weights according to the characteristics of the density values of the original image to the coefficients of the high-frequency components for each level of some or all of the plurality of levels of the multi-resolution decomposition;
An image processing apparatus comprising: reconstructing means for reconstructing the coefficient data having the weighted high-frequency component coefficients into a new image.

The decomposing means is means for decomposing the original image into subbands having the coefficient data by performing the multi-resolution decomposition of the plurality of levels by wavelet transform,
The image processing apparatus according to claim 1, wherein the reconstruction unit is a unit that performs inverse wavelet transform on the subbands weighted by the weighting unit to reconstruct the new image.

The density shift means is a means for shifting any one of an average density value, a median value, a mode value, and an average value of a maximum value and a minimum value of the pixels of the original image on the density gradation. The image processing apparatus according to claim 1, wherein the image processing apparatus is provided.

The weight, the desired value alpha ₀ at the level j = 1 of the wavelet transform _(> 1) Ri adopt the highest level or the highest level below the desired level (level the level j depends on the matrix size of the original image 4. The image processing apparatus according to claim 2, wherein the value is determined based on a monotonous non-increasing function in accordance with an increase in the level j so that 1 is taken in (except for 1).

Monotonically non-increasing function of said weight, said from the desired value alpha ₀ when the constant function constant become remains of the desired value alpha ₀ when the value of the level j is increased, the value of the level j is increased 5. The image processing apparatus according to claim 4 , wherein the image processing apparatus is one selected from a function including a highest level or a monotone decreasing function that is 1 at the desired level.

Said weighting means is configured to automatically calculate the desired value alpha _0, one of the multiple levels constant weight or the monotonically decreasing function is the desired value alpha ₀ which is determined by the constant function to the high-frequency components of the respective The image processing apparatus according to claim 4 , wherein the non-constant weight determined by is selectively given.

The weighting unit accepts the desired value α ₀ given as an arbitrary value from an operator, and the constant weight or the monotonic decrease that is the desired value α ₀ determined by the constant function for the high-frequency component of each of the plurality of levels. The image processing apparatus according to claim 4 , wherein the image processing apparatus is a unit that selectively gives a non-constant weight determined by any one of the functions.

The weight monotonically decreasing function is as follows: (i): As the level increases, the weight gradually decreases, then decreases rapidly, and then gradually decreases again to increase the level. A function that decreases so as to draw an S-shaped trajectory as compared to a straight line that decreases in direct proportion; to function, or, (iii): as the level increases, to claim 4, wherein the degree of decrease of the weight is one of the function to be reduced so as to draw progressively becomes smaller curve The image processing apparatus described.

The weighting means includes a characteristic determination means for determining a characteristic of the density value of the original image, a selection means for automatically selecting the constant weight or the non-constant weight according to the determination result by the characteristic determination means, The image processing apparatus according to claim 3 , further comprising weighting execution means for executing weighting processing of the constant weight or non-constant weight selected by the selection means. .

The density shift unit and the feature determination unit are configured to execute the calculation of the average density and the feature determination of the density value respectively for the entire area or the same partial area of the original image. The image processing apparatus according to claim 9 .

The image processing apparatus according to claim 1 , wherein the original image is an image of a subject collected by a medical image diagnostic apparatus.

In an image processing method for enhancing contrast of an original image composed of pixels having digitized density values,
Subjecting the image data of the original image to multi-resolution decomposition to decompose into coefficient data composed of coefficients of a low frequency component and a high frequency component;
Assigning weights according to the characteristics of the density values of the original image to the coefficients of the high-frequency component for each level for some or all of the multiple resolution decomposition levels;
Reconstructing the coefficient data having the weighted high-frequency component coefficients into a new image.

The decomposing step is a step of decomposing the original image into subbands having the coefficient data by performing multi-resolution decomposition of a plurality of levels by wavelet transform,
13. The image processing method according to claim 12 , wherein the reconstructing step is a step of reconstructing the new image by performing inverse wavelet transform on the weighted subband.

Prior to the decomposing step, an average density value, a median value, a mode value, and an average value of a maximum value and a minimum value of pixels of the original image are given as the gray level. The image processing method according to claim 13 , wherein a step of shifting on the density gradation is set as preprocessing.

A program for causing a computer to execute processing for enhancing contrast of an original image composed of pixels having digitized density values,
The computer,
Decomposition means for decomposing the image data of the original image into multi-resolution decomposition into coefficient data composed of coefficients of a low frequency component and a high frequency component;
Weighting means for assigning weights according to the characteristics of the density values of the original image to the coefficients of the high-frequency components for each level of some or all of the plurality of levels of the multi-resolution decomposition;
A program that functions as reconstruction means for reconstructing the coefficient data having the weighted high-frequency component coefficients into a new image.