Companion Website: Digital Image Processing, 2/E aracer.mobi gonzalezwoods. Digital Image Processing, 2/E is a completely self-contained book. The. Completely self-contained—and heavily illustrated—this introduction to basic concepts and methodologies for digital image processing is. Digital Image Processing, 3rd ed. aracer.mobi Gonzalez & Woods. Chapter 2. Digital Image Fundamentals. Chapter 2. Digital Image.
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Digital image processing by Rafael C. Gonzalez, Richard E. Woods, 2nd Edition. Irfan jamil. Uploaded by. Irfan jamil. Loading Preview. Sorry, preview is. Digital Image Processing, 3rd Edition,Instructor's Manual,Rafael C. Gonzalez. Douglas Sun. Instructor's Manual NOTICE This manual is intended for your. Digital Image Processing 2nd ed - aracer.mobiez - Free ebook download as PDF File .pdf) or read book online for free.
Completely self-contained--and heavily illustrated--this introduction to basic concepts and methodologies for digital image processing is written at a level that truly is suitable for seniors and first-year graduate students in almost any technical discipline. The leading textbook in its field for more than twenty years, it continues its cutting-edge focus on contemporary developments in all mainstream areas of image processing--e.
It focuses on material that is fundamental and has a broad scope of application.
Gonzalez received the B. He served as Chairman of the department from through New to this Edition: This edition of Digital Image Processing is a major revision and is based on the most extensive survey the authors have ever conducted.
The survey involved faculty, students, and independent readers of the book in institutions from 32 countries. The results have prompted the following new and reorganized material: Expanded homework sets, including over 80 new problems. The averaging mask has n 2 points of which we are assuming that q 2 points are from the object and the rest from the background. Note that this assumption implies separation be- tween objects that, at a minimum, is equal to the area of the mask all around each object.
The problem becomes intractable unless this assumption is made. This condition was not given in the problem statement on purpose in order to force the student to arrive at that conclusion. If the instructor wishes to simplify the problem, this should then be mentioned when the problem is assigned. A further simplification is to tell the students that the intensity level of the back- ground is 0.
Let B represent the intensity level of background pixels, let a i denote the in- tensity levels of points inside the mask and o i the levels of the objects.
In addi- tion, let S a denote the set of points in the averaging mask, So the set of points in the object, and S b the set of points in the mask that are not object points. Let the maximum expected average value of object points be denoted by Q max. If this was a fact specified by the instructor, or the student made this assumption from the beginning, then this answer follows almost by inspection.
We want to show that the right sides of the first two equations are equal. All other elements are 0. This mask will perform differentiation in only one direction, and will ignore intensity transitions in the orthogonal direc- tion. An image processed with such a mask will exhibit sharpening in only one direction.
A Laplacian mask with a -4 in the center and 1s in the vertical and horizontal directions will obviously produce an image with sharpening in both directions and in general will appear sharper than with the previous mask. In other words, the number of coefficients and thus size of the mask is a direct result of the definition of the second derivative.
In fact, as explained in part b , just the opposite occurs. To see why this is so, consider an image consisting of two vertical bands, a black band on the left and a white band on the right, with the transition be- tween the bands occurring through the center of the image. That is, the image has a sharp vertical edge through its center. As the center of the mask moves more than two pixels on either side of the edge the entire mask will en- compass a constant area and its response would be zero, as it should.
However, suppose that the mask is much larger. As its center moves through, say, the black 0 area, one half of the mask will be totally contained in that area.
However, de- pending on its size, part of the mask will be contained in the white area. The sum of products will therefore be different from 0. This means that there will be a response in an area where the response should have been 0 because the mask is centered on a constant area.
The progressively increasing blurring as a result of mask size is evident in these results. Convolv- ing f x , y with the mask in Fig.
Then, because these operations are linear, we can use superposition, and we see from the preceding equation that using two masks of the form in Fig. Convolving this mask with f x , y produces g x , y , the unsharp result. The right side of this equation is recognized within the just-mentioned propor- tionality factors to be of the same form as the definition of unsharp masking given in Eqs. Thus, it has been demonstrated that subtract- ing the Laplacian from an image is proportional to unsharp masking.
The fact that images stay in the linear range implies that images will not be saturated at the high end or be driven in the low end to such an extent that the camera will not be able to respond, thus losing image information irretrievably. The only way to establish a benchmark value for illumination is when the variable daylight illumination is not present.
Let f 0 x , y denote an image taken under artificial illumination only, with no moving objects e. This be- comes the standard by which all other images will be normalized. There are nu- merous ways to solve this problem, but the student must show awareness that areas in the image likely to change due to moving objects should be excluded from the illumination-correction approach.
One way is to select various representative subareas of f 0 x , y not likely to be obscured by moving objects and compute their average intensities.
We then select the minimum and maximum of all the individual average values, denoted by, f min and f max. The objective then is to process any input image, f x , y , so that its minimum and maximum will be equal to f min and f max , respectively.
Another implicit assumption is that moving objects com- prise a relatively small area in the field of view of the camera, otherwise these objects would overpower the scene and the values obtained from f 0 x , y would not make sense.
If the student selects another automated approach e. We support this conclusion with an example. Consider a one-pixel-thick straight black line running vertically through a white image. As the size of the neighborhood increases, we would have to be further and further from the line before the center point ceases to be called a boundary point.
That is, the thickness of the boundary detected increases as the size of the neighbor- hood increases. If the intensity is smaller than the intensity of all its neighbors, then increase it. Else, do not nothing. In rule 1, all positive differences mean that the intensity of the noise pulse z 5 is less than that of all its 4-neighbors. The converse is true when all the differences are negative.
A mixture of positive and negative differences calls for no action because the center pixel is not a clear spike. In this case the correction should be zero keep in mind that zero is a fuzzy set too.
Membership function ZR is also a triangle. It is centered on 0 and overlaps the other two slightly. This diagram is similar to Fig. This rule is nothing more that computing 1 minus the minimum value of the outputs of step 2, and using the result to clip the ZR membership function. It is important to understand that the output of the fuzzy system is the center of gravity of the result of aggregation step 4 in Fig.
This would produce the complete ZR membership function in the implication step step 3 in Fig. The other two results would be zero, so the result of aggregation would be the ZR function. This is as it should be because the differences are all positive, indicating that the value of z 5 is less than the value of its 4-neighbors.
Fuzzify inputs. Apply fuzzy logical 3. Apply d2 d4 d6 d8 aggregation method max. Defuzzify center of v gravity. It is a phase term that accounts for the shift in the function. The magnitude of the Fourier transform is the same in both cases, as expected. The last step follows from Eq. Problem 4. The continuous Fourier trans- form of the given sine wave looks as in Fig. In terms of Fig. For some values of sampling, the sum of the two sines combine to form a single sine wave and a plot of the samples would appear as in Fig.
Other values would result in functions whose samples can describe any shape obtainable by sampling the sum of two sines. But, we know from the translation property Table 4. This proves that multiplication in the frequency domain is equal to convolution in the spatial domain.
The proof that multiplication in the spatial domain is equal to convolution in the spatial domain is done in a similar way.
Because, by the convolution theorem, the Fourier transform of the spatial convolution of two functions is the product their transforms, it follows that the Fourier transform of a tent function is a sinc func- tion squared. Substitut- ing Eq.
Substituting Eq. We do this by direct substitution into Eq. Note that this holds for positive and negative values of k. We prove the validity of Eq. The other half of the discrete convolution theorem is proved in a similar manner. To avoid aliasing we have to sample at a rate that exceeds twice this frequency or 2 0. So, each square has to correspond to slightly more than one pixel in the imaging system. This is not the case in zooming, which introduces additional samples.
Although no new detail in introduced by zooming, it certainly does not reduce the sampling rate, so zooming cannot result in aliasing. The linearity of the inverse transforms is proved in exactly the same way. There are various ways of proving this.
The vector is cen- tered at the origin and its direction depends on the value of the argument. This means that the vector makes an integer num- ber of revolutions about the origin in equal increments.
This produces a zero sum for the real part of the exponent. Similar comments apply the imaginary part. Proofs of the other properties are given in Chapter 4. Recall that when we refer to a function as imaginary, its real part is zero. We use the term complex to denote a function whose real and imaginary parts are not zero. We prove only the forward part the Fourier transform pairs. Similar techniques are used to prove the inverse part. Because f x , y is imaginary, we can express it as j g x , y , where g x , y is a real function.
Then the proof is as follows: And conversely. From Example 4. If f x , y is real and odd, then F u , v is imaginary and odd, and conversely. Because f x , y is real, we know that the real part of F u , v is even and its imaginary part is odd.
If we can show that F is purely imaginary, then we will have completed the proof. If f x , y is imaginary and even, then F u , v is imaginary and even, and conversely. We know that when f x , y is imaginary, then the real part of F u , v is odd and its imaginary part is even. If we can show that the real part is 0, then we will have proved this property.
Because f x , y is imagi- nary, we can express it as j g x , y , where g is a real function. If f x , y is imaginary and odd, then F u , v is real and odd, and conversely.
If f x , y is imaginary, we know that the real part of F u , v is odd and its imaginary part is even. If f x , y is complex and even, then F u , v is complex and even, and conversely. Here, we have to prove that both the real and imaginary parts of F u , v are even.
Recall that if f x , y is an even function, both its real and imaginary parts are even. The second term is the DFT of a purely imaginary even function, which we know is imaginary and even.
Thus, we see that the the transform of a complex, even function, has an even real part and an even imaginary part, and is thus a complex even function. This concludes the proof. The proof parallels the proof in h. The second term is the DFT of purely imaginary odd function, which we know is real and odd.
Thus, the sum of the two is a complex, odd function, as we wanted to prove. Imagine the image on the left being duplicated in- finitely many times to cover the x y -plane. The result would be a checkerboard, with each square being in the checkerboard being the image and the black ex- tensions.
Now imagine doing the same thing to the image on the right. The results would be identical. Thus, either form of padding accomplishes the same separation between images, as desired.
These can be strong horizontal and vertical edges.
These sharp transitions in the spatial domain introduce high-frequency components along the vertical and horizontal axes of the spectrum. This is as expected; padding an image with zeros decreases its average value. The last step follows from the fact that k 1 x and k 2 y are integers, which makes the two rightmost exponentials equal to 1. The other part of the convolution theorem is done in a similar manner. Consider next the second derivative.
We can generate a filter for using with the DFT simply by sampling this function: In summary, we have the following Fourier transform pair relating the Laplacian in the spatial and frequency domains: Thus, we see that the amplitude of the filter decreases as a function of distance from the origin of the centered filter, which is the characteristic of a lowpass filter.
A similar argument is easily carried out when considering both variables simultaneously. From property 3 in Table 4. The negative limiting value is due to the order in which the derivatives are taken. The important point here is that the dc term is eliminated and higher frequencies are passed, which is the characteristic of a highpass filter. As in Problem 4. For val- ues away from the center, H u , v decreases as in Problem 4.
The important point is the the dc term is eliminated and the higher frequencies are passed, which is the characteristic of a highpass filter. The Fourier transform is a linear process, while the square and square roots involved in computing the gradient are nonlinear operations.
The Fourier transform could be used to compute the derivatives as differences as in Problem 4. The explanation will be clearer if we start with one variable.
This result is for continuous functions. To use them with discrete variables we simply sample the function into its desired dimensions. The inverse Fourier transform of 1 gives an impulse at the origin in the highpass spatial filters. However, the dark center area is averaged out by the lowpass filter. The reason the final result looks so bright is that the discontinuity edge on boundaries of the ring are much higher than anywhere else in the image, thus dominating the display of the result.
The order does not matter. We know that this term is equal to the average value of the image. So, there is a value of K after which the result of repeated lowpass filtering will simply produce a constant image. Note that the answer applies even as K approaches infinity. In this case the filter will ap- proach an impulse at the origin, and this would still give us F 0, 0 as the result of filtering. We want all values of the filter to be zero for all values of the distance from the origin that are greater than 0 i.
However, the filter is a Gaussian function, so its value is always greater than 0 for all finite values of D u , v. But, we are dealing with digital numbers, which will be designated as zero whenever the value of the filter is less than one-half the smallest positive number representable in the computer being used. As given in the problem statement, the value of this number is c min. So, values of K for which for which the filter function is greater than 0.
Because the exponential decreases as a function of increasing distance from the origin, we choose the smallest possible value of D 2 u , v , which is 1. This result guarantees that the lowpass filter will act as a notch pass filter, leaving only the value of the trans- form at the origin.
The image will not change past this value of K. The solution to the problem parallels the solution of Problem 4. Here, however, the filter will approach a notch filter that will take out F 0, 0 and thus will produce an image with zero average value this implies negative pixels. So, there is a value of K after which the result of repeated highpass filtering will simply produce a constant image. We want all values of the filter to be 1 for all values of the distance from the origin that are greater than 0 i.
This is the same requirement as in Problem 4. Although high-frequency emphasis helps some, the improve- ment is usually not dramatic see Fig. Thus, if an image is histogram equalized first, the gain in contrast improvement will essentially be lost in the fil- tering process. Therefore, the procedure in general is to filter first and histogram- equalize the image after that.
The preceding equation is easily modified to accomplish this: Next, we assume that the equations hold for n. From this result, it is evident that the contribution of illumination is an impulse at the origin of the frequency plane. A notch filter that attenuates only this com- ponent will take care of the problem.
Extension of this development to multiple impulses stars is implemented by considering one star at a time. The form of the filter will be the same. At the end of the procedure, all individual images are combined by addition, followed by intensity scaling so that the relative bright- ness between the stars is preserved.
Perform a median filtering operation. Follow 1 by high-frequency emphasis. Histogram-equalize this result. Compute the average gray level, K 0.
Perform the transformations shown in Fig. Figure P5. Problem 5. Draw a profile of an ideal edge with a few points valued 0 and a few points valued 1.
The geometric mean will give only values of 0 and 1, whereas the arithmetic mean will give intermediate values blur. Because the center of the mask can be outside the original black area when this happens, the figure will be thickened.
For the noise spike to be visible, its value must be considerably larger than the value of its neighbors. Also keep in mind that the power in the numerator is 1 plus the power in the denominator.
It is most visible when surrounded by light values. The center pixel the pepper noise , will have little influence in the sums.
If the area spanned by the filter is approximately con- stant, the ratio will approach the value of the pixels in the neighborhood—thus reducing the effect of the low-value pixel.
The center pixel will now be the largest. However, the exponent is now negative, so the small numbers will dominate the result.
That constant is the value of the pixels in the neighborhood.
So the ratio is just that value. For salt noise the image will become very light. The opposite is true for pepper noise—the image will become dark. The terms of the sum in the de- nominator are 1 divided by individual pixel values in the neighborhood. Thus, low pixel values will tend to produce low filter responses, and vice versa. If, for example, the filter is centered on a large spike surrounded by zeros, the response will be a low output, thus reducing the effect of the spike.
The Fourier transform of the 1 gives an impulse at the origin, and the exponentials shift the origin of the impulse, as discussed in Section 4.
Then, the components of motion are as follows: They can be found, for example, the Handbook of Mathematical Functions, by Abramowitz, or other similar ref- erence. Any of the techniques dis- cussed in this chapter for handling uniform blur along one dimension can then be applied to the problem. The image is then converted back to rectangular co- ordinates after restoration. The mathematical solution is simple. Any of the methods in Sections 5.
Set all pixels in the image, ex- cept the cross hairs, to that intensity value. Denote the Fourier transform of this image by G u , v. Because the characteristics of the cross hairs are given with a high degree of accuracy, we can construct an image of the background of the same size using the background intensity levels determined previously.
We then construct a model of the cross hairs in the correct location determined from the given image using the dimensions provided and intensity level of the cross hairs. Denote by F u , v the Fourier transform of this new image. In the likely event of vanishing values in F u , v , we can construct a radially-limited filter us- ing the method discussed in connection with Fig. Because we know F u , v and G u , v , and an estimate of H u , v , we can refine our estimate of the blur- ring function by substituting G and H in Eq.
The resulting filter in either case can then be used to deblur the image of the heart, if desired. But, we know from the statement of Problem 4. Therefore, we have reduced the problem to computing the Fourier transform of a Gaussian function. From the basic form of the Gaussian Fourier transform pair given in entry 13 of Table 4.
Keep in mind that the preceding derivations are based on assuming continuous variables. A discrete filter is obtained by sampling the continuous function. Its purpose is to gain familiarity with the vari- ous terms of the Wiener filter. This is as far as we can reasonably carry this problem. It is worthwhile pointing out to students that a filter in the frequency domain for the Laplacian operator is discussed in Section 4.
However, substituting that solution for P u , v here would only increase the number of terms in the filter and would not help in simplifying the expression. Furthermore, we can use superposition and obtain the response of the system first to F u , v and then to N u , v because we know that the image and noise are uncorrelated.
The sum of the two individual responses then gives the complete response. The principal steps are as follows: Select coins as close as possible in size and content as the lost coins. Select a background that approximates the texture and brightness of the photos of the lost coins. Set up the museum photographic camera in a geometry as close as possi- ble to give images that resemble the images of the lost coins this includes paying attention to illumination.
Obtain a few test photos. To simplify experimentation, obtain a TV camera capable of giving images that re- semble the test photos. This can be done by connecting the camera to an image processing system and generating digital images, which will be used in the experiment. Obtain sets of images of each coin with different lens settings.
The re- sulting images should approximate the aspect angle, size in relation to the area occupied by the background , and blur of the photos of the lost coins. The lens setting for each image in 3 is a model of the blurring process for the corresponding image of a lost coin. Digitize the impulse. Its Fourier transform is the transfer function of the blurring process. Digitize each blurred photo of a lost coin, and obtain its Fourier trans- form.
At this point, we have H u , v and G u , v for each coin. Obtain an approximation to F u , v by using a Wiener filter. Equation 5. In general, several experimental passes of these basic steps with various different settings and parameters are required to obtain acceptable results in a problem such as this. The intensity at that point is double the intensity of all other points. From the definition of the Radon transform in Eq. We do this by substituting the convolution expression into Eq.
This completes the proof. Chapter 6 Problem Solutions Problem 6. These are the trichromatic coefficients. We are interested in tristimulus values X , Y , and Z , which are related to the trichromatic coefficients by Eqs.
Note however, that all the tristimulus coefficients are divided by the same constant, so their percentages relative to the trichromatic coefficients are the same as those of the coefficients. Problem 6. Values in between are easily seen to follow from these simple relations. The key to solving this problem is to realize that any color on the border of the triangle is made up of proportions from the two vertices defining the line segment that contains the point.
The line segment connecting points c 3 and c is shown extended dashed seg- ment until it intersects the line segment connecting c 1 and c 2. The point of in- tersection is denoted c 0. Because we have the values of c 1 and c 2 , if we knew c 0 , we could compute the percentages of c 1 and c 2 contained in c 0 by using the method described in Problem 6. Let the ratio of the content of c 1 and c 2 in c 0 be denoted by R If we now add color c 3 to c 0 , we know from Problem 6.
For any position of a point along this line we could determine the percentage of c 3 and c 0 , again, by using the method described in Problem 6. What is important to keep in mind that the ratio R 12 will remain the same for any point along the segment connect- ing c 3 and c 0. The color of the points along this line is different for each position, but the ratio of c 1 to c 2 will remain constant. So, if we can obtain c 0 , we can then determine the ratio R 12 , and the percent- age of c 3 , in color c.
The point c 0 is not difficult to obtain. The intersection of these two lines gives the coordinates of c 0. The lines can be determined uniquely because we know the coordinates of the two point pairs needed to determine the line coefficients.
Solving for the intersec- tion in terms of these coordinates is straightforward, but tedious. Our interest here is in the fundamental method, not the mechanics of manipulating simple equations so we do not give the details. At this juncture we have the percentage of c 3 and the ratio between c 1 and c 2. Let the percentages of these three colors composing c be denoted by p 1 , p 2 , and p 3 respectively. Finally, note that this problem could have been solved the same way by intersecting one of the other two sides of the triangle.
Going to another side would be necessary, for example, if the line we used in the preceding discussion had an infinite slope. A simple test to determine if the color of c is equal to any of the vertices should be the first step in the procedure; in this case no additional calculations would be required. With a specific filter in place, only the objects whose color cor- responds to that wavelength will produce a significant response on the mono- chrome camera.
A motorized filter wheel can be used to control filter position from a computer. If one of the colors is white, then the response of the three filters will be approximately equal and high.
If one of the colors is black, the response of the three filters will be approximately equal and low. We can create Table P6. Thus, we get the monochrome displays shown in Fig. For a color to be gray, all RGB components have to be equal, so there are shades of gray. The others decrease in saturation from the corners toward the black or white point.
Table P6. From left to right, the color bars are in accordance with Fig. The middle gray background is unchanged. Figure P6. For clarity, we will use a prime to denote the CMY components. And from Eq. Note that, in accordance with Eq. Thus, we get the monochrome display shown in Fig. To generate a color rectangle with the properties required in the problem statement, we choose a fixed intensity I , and maximum saturation these are spectrum colors, which are supposed to be fully saturated , S.
If we have more than eight bits, then the increments can be smaller. Longer strips also can be made by duplicating column values. One is to approach it in the HSI space and the other is to use polar coordinates to create a hue image whose values grow as a function of angle. The center of the image is the middle of what- ever image area is used.
Values of the saturation image decrease linearly in all radial directions from the origin. The intensity image is just a specified constant. With these basics in mind it is not difficult to write a program that generates the desired result. It also is given that the gray-level images in the problem statement are 8-bit images.
The latter condition means that hue angle can only be divided into a maximum number of values. Another way of looking at this is that the entire [0, ] hue scale is compressed to the range [0, ]. From this we easily compute the values of the other two regions as being and The region in Figure P6. This also is true of the black background.
The region in the center of the color image is white, so its saturation is 0. Therefore, the value of both darker gray regions in the intensity image have value 85 i.
Similarly, equal proportions of the secondaries yellow, cyan, and ma- genta produce white, so the two lighter gray regions have the same value as the region shown in the figure. The center of the image is white, so its value is Threshold the image with a threshold value slightly larger than 0.
The result is shown in Fig. It is clear that coloring all the black points in the desired shade of blue presents no difficulties. We already know how to take out the water from b. Re- moval of the red [and the black if you do not want to use the method as in b ] can be done by using the technique discussed in Section 6. This was demonstrated in Problem 6. That is, as long as any one of the RGB components is 0, Eq.
Consider RGB colors 1, 0, 0 and 0, 0. The HSI triplets for these colors [per Eq. Their HSI values [per Eqs. Saturation alone is not enough informa- tion to compute the saturation of the complemented color.
The hue component is the angle from red in a counterclockwise direction normalized by degrees. For a color on the top half of the circle i. For a color on the bottom half of the circle i. But from the definition of the CMY space in Eq. The red, green, and blue components should be transformed with the same mapping function so that the colors do not change. The general shape of the curve would be as shown in Fig. The computations are best done in a spreadsheet, as shown in Table P6.
Assume that the component image values of the HSI image are in the range [0, 1].
Call the component images H hue , S saturation , and I intensity. Similarly, all the squares are at their maximum value so, from Eq. The hue component image, H , is shown in Fig. Recall from Fig. Thus, the important point to be made in Fig.
As you can see, this indeed is the case for the squares in Fig. For the shades of red, green, and blue in Fig. When the aver- aging mask is fully contained in a square, there is no blurring because the value of each square is constant.
This book was written for just this purpose. Its main objective is to provide a foundation for implementing image processing algorithms using modern software tools. To achieve these objectives, we felt that two key ingredients were needed.
The first was to select image processing material that is representative of material covered in a formal course of instruction in this field.
The second was to select software tools that are well supported and documented, and which have a wide range of applications in the real world. To meet the first objective, most of the theoretical concepts in the following chapters were selected from Digital Image Processing by Gonzalez and Woods, which has been the choice introductory textbook used by educators all over the world for over two decades.
A basic strategy followed in the preparation of the book was to provide a seamless integration of well-established theoretical concepts and their implementation using state-of-the-art software tools. The book is organized along the same lines as Digital Image Processing. In this way, the reader has easy access to a more detailed treatment of all the image processing concepts discussed here, as well as an up-to-date set of references for further reading. Following this approach made it possible to present theoretical material in a succinct manner and thus we were able to maintain a focus on the software implementation aspects of image processing problem solutions.