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<doc>
   <title>Image Processing</title>

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   <body>
      <br/><br/>

         <p>
            This page documents the functionality present in this library that deals with the
            management and manipulation of images.  One thing to note is that there is no 
            explicit image object.  Instead, everything deals with <a href="containers.html#array2d">
            array2d</a> objects that contain various kinds of pixels.  
         </p>

   </body>

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   <menu width="150">
    <top>

      <section>
         <name>Pixels</name>
         <item>rgb_pixel</item>
         <item>bgr_pixel</item>
         <item>cv_image</item>
         <item>rgb_alpha_pixel</item>
         <item>hsi_pixel</item>
         <item>pixel_traits</item>
         <item>get_pixel_intensity</item> 
         <item>assign_pixel</item> 
         <item>assign_pixel_intensity</item> 
      </section>

      <section>
         <name>Image I/O</name>
         <item>png_loader</item>
         <item>jpeg_loader</item>
         <item>load_bmp</item> 
         <item>save_bmp</item> 
         <item>load_dng</item> 
         <item>save_dng</item> 
      </section>

      <section>
         <name>Keypoints and Descriptors</name>

         <item>integral_image</item>
         <item>hessian_pyramid</item>
         <item>compute_dominant_angle</item>
         <item>compute_surf_descriptor</item>
         <item>hog_image</item>
         <item>haar_x</item>
         <item>haar_y</item>
         <item>get_interest_points</item>
         <item>get_surf_points</item>
         <item>interest_point</item>
         <item>surf_point</item>
      </section>

      <section>
         <name>Edges and Thresholds</name>
         <item>edge_orientation</item> 
         <item>hysteresis_threshold</item> 
         <item>sobel_edge_detector</item> 
         <item>suppress_non_maximum_edges</item> 
         <item>threshold_image</item>
         <item>auto_threshold_image</item>
      </section>
 
      <section>
         <name>Miscellaneous</name>

         <item>draw_line</item> 
         <item>assign_image</item> 
         <item>assign_image_scaled</item> 
         <item>assign_all_pixels</item> 
         <item>assign_border_pixels</item> 
         <item>equalize_histogram</item> 
         <item>get_histogram</item> 
         <item>spatially_filter_image</item> 
         <item>pyramid_down</item> 
         <item>zero_border_pixels</item> 

         <item>binary_dilation</item>
         <item>binary_erosion</item>
         <item>binary_open</item>
         <item>binary_close</item>
         <item>binary_intersection</item>
         <item>binary_union</item>
         <item>binary_difference</item>
         <item>binary_complement</item>
      </section>

    </top>  
   </menu>

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   <components>
   
   <!-- ************************************************************************* -->
      
      <component>
         <name>integral_image</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/integral_image_abstract.h</spec_file>
         <description>
                This object is an alternate way of representing image data
                that allows for very fast computations of sums of pixels in 
                rectangular regions.  To use this object you load it with a
                normal image and then you can use the get_sum_of_area()
                member function to compute sums of pixels in a given area in
                constant time.
         </description>
                                 
      </component>

   <!-- ************************************************************************* -->
      
      <component>
         <name>haar_x</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/integral_image_abstract.h</spec_file>
         <description>
            This is a function that operates on an <a href="#integral_image">integral_image</a>
            and allows you to compute the response of a Haar wavelet oriented along
            the X axis.  
         </description>
                                 
      </component>

   <!-- ************************************************************************* -->
      
      <component>
         <name>haar_y</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/integral_image_abstract.h</spec_file>
         <description>
            This is a function that operates on an <a href="#integral_image">integral_image</a>
            and allows you to compute the response of a Haar wavelet oriented along
            the Y axis.  
         </description>
                                 
      </component>

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      <component>
         <name>compute_dominant_angle</name>
         <file>dlib/image_keypoint.h</file>
         <spec_file link="true">dlib/image_keypoint/surf_abstract.h</spec_file>
         <description>
            Computes and returns the dominant angle (i.e. the angle of the dominant gradient)
            at a given point and scale in an image.   This function is part of the
            main processing of the SURF algorithm.
         </description>
                                 
      </component>

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      <component>
         <name>get_surf_points</name>
         <file>dlib/image_keypoint.h</file>
         <spec_file link="true">dlib/image_keypoint/surf_abstract.h</spec_file>
         <description>
             This function runs the complete SURF algorithm on an input image and 
             returns the points it found.  For a description of what exactly
             the SURF algorithm does you should read the following paper:
             <blockquote>
               SURF: Speeded Up Robust Features
               By Herbert Bay, Tinne Tuytelaars, and Luc Van Gool
             </blockquote>
             <p>
                Also note that there are numerous flavors of the SURF algorithm
                you can put together using the functions in dlib.  The get_surf_points()
                function is just an example of one way you might do so.  
             </p>
         </description>
         <examples>
            <example>surf_ex.cpp.html</example>
         </examples>
                                 
      </component>

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      <component>
         <name>compute_surf_descriptor</name>
         <file>dlib/image_keypoint.h</file>
         <spec_file link="true">dlib/image_keypoint/surf_abstract.h</spec_file>
         <description>
            Computes the 64 dimensional SURF descriptor vector of a box centered
              at a given center point, tilted at a given angle, and sized according to 
              a given scale.  
         </description>
                                 
      </component>

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      <component>
         <name>hog_image</name>
         <file>dlib/image_keypoint.h</file>
         <spec_file link="true">dlib/image_keypoint/hog_abstract.h</spec_file>
         <description>
                This object is a tool for performing the image feature extraction algorithm
                described in the following paper:
                <blockquote>
                    Histograms of Oriented Gradients for Human Detection
                    by Navneet Dalal and Bill Triggs
                </blockquote>
         </description>
                                 
      </component>

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      <component>
         <name>hessian_pyramid</name>
         <file>dlib/image_keypoint.h</file>
         <spec_file link="true">dlib/image_keypoint/hessian_pyramid_abstract.h</spec_file>
         <description>
                This object represents an image pyramid where each level in the
                pyramid holds determinants of Hessian matrices for the original 
                input image.  This object can be used to find stable interest
                points in an image.  

               <br/><br/>
                This object is an implementation of the fast Hessian pyramid 
                as described in the paper: 
                <blockquote>
                   SURF: Speeded Up Robust Features
                   By Herbert Bay, Tinne Tuytelaars, and Luc Van Gool
                </blockquote>

                This implementation was also influenced by the very well documented
                OpenSURF library and its corresponding description of how the fast
                Hessian algorithm functions:  
                <blockquote>Notes on the OpenSURF Library by Christopher Evans</blockquote>
         </description>
                                 
      </component>

   <!-- ************************************************************************* -->
      
      <component>
         <name>get_interest_points</name>
         <file>dlib/image_keypoint.h</file>
         <spec_file link="true">dlib/image_keypoint/hessian_pyramid_abstract.h</spec_file>
         <description>
            This function extracts interest points from a <a href="#hessian_pyramid">hessian_pyramid</a>.
         </description>
                                 
      </component>

   <!-- ************************************************************************* -->
      
      <component>
         <name>interest_point</name>
         <file>dlib/image_keypoint.h</file>
         <spec_file link="true">dlib/image_keypoint/hessian_pyramid_abstract.h</spec_file>
         <description>
            This is a simple struct used to represent the interest points returned
            by the <a href="#get_interest_points">get_interest_points</a> function.
         </description>
                                 
      </component>

   <!-- ************************************************************************* -->
      
      <component>
         <name>surf_point</name>
         <file>dlib/image_keypoint.h</file>
         <spec_file link="true">dlib/image_keypoint/surf_abstract.h</spec_file>
         <description>
            This is a simple struct used to represent the SURF points returned
            by the <a href="#get_surf_points">get_surf_points</a> function.
         </description>
         <examples>
            <example>surf_ex.cpp.html</example>
         </examples>
                                 
      </component>

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      <component>
         <name>pixel_traits</name>
         <file>dlib/pixel.h</file>
         <spec_file>dlib/pixel.h</spec_file>
         <description>
            As the name implies, this is a traits class for pixel types. It allows you
            to determine what sort of pixel type you are dealing with.
         </description>
                                 
      </component>
            
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      <component>
         <name>hsi_pixel</name>
         <file>dlib/pixel.h</file>
         <spec_file link="true">dlib/pixel.h</spec_file>
         <description>
            This is a simple struct that represents an HSI colored graphical pixel.  
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>rgb_alpha_pixel</name>
         <file>dlib/pixel.h</file>
         <spec_file link="true">dlib/pixel.h</spec_file>
         <description>
            This is a simple struct that represents an RGB colored graphical pixel with an 
            alpha channel.  
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>rgb_pixel</name>
         <file>dlib/pixel.h</file>
         <spec_file link="true">dlib/pixel.h</spec_file>
         <description>
            This is a simple struct that represents an RGB colored graphical pixel.  
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>bgr_pixel</name>
         <file>dlib/pixel.h</file>
         <spec_file link="true">dlib/pixel.h</spec_file>
         <description>
            This is a simple struct that represents a BGR colored graphical pixel.  
            <p>
            The difference between this object and the <a href="#rgb_pixel">rgb_pixel</a>
            is just that this struct lays its pixels down in memory in BGR order rather
            than RGB order.  You only care about this if you are doing something like
            using the <a href="#cv_image">cv_image</a> object to map an OpenCV image
            into a more object oriented form.
            </p>
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>cv_image</name>
         <file>dlib/opencv.h</file>
         <spec_file link="true">dlib/opencv/cv_image_abstract.h</spec_file>
         <description>
            This object is meant to be used as a simple wrapper around the OpenCV
            IplImage struct.  Using this class template you can turn an IplImage
            object into something that looks like a normal dlib style image object.

            <p>
            So you should be able to use cv_image objects with many of the image
            processing functions in dlib as well as the GUI tools for displaying
            images on the screen.
            </p>
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>assign_pixel</name>
         <file>dlib/pixel.h</file>
         <spec_file link="true">dlib/pixel.h</spec_file>
         <description>
            assign_pixel() is a templated function that can assign any pixel type to another pixel type.
            It will perform whatever conversion is necessary to make the assignment work.  (E.g. color to 
            grayscale conversion)
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>assign_pixel_intensity</name>
         <file>dlib/pixel.h</file>
         <spec_file link="true">dlib/pixel.h</spec_file>
         <description>
            assign_pixel_intensity() is a templated function that can change the
            intensity of a pixel.  So if the pixel in question is a grayscale pixel
            then it simply assigns that pixel the given value.  However, if the
            pixel is not a grayscale pixel then it converts the pixel to the
            HSI color space and sets the I channel to the given intensity
            and then converts this HSI value back to the original pixel's 
            color space.
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>get_pixel_intensity</name>
         <file>dlib/pixel.h</file>
         <spec_file link="true">dlib/pixel.h</spec_file>
         <description>
            get_pixel_intensity() is a templated function that 
            returns the grayscale intensity of a pixel.  If the pixel isn't a grayscale
            pixel then it converts the pixel to the HSI color space and returns the
            obtained intensity value.
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>png_loader</name>
         <file>dlib/image_io.h</file>
         <spec_file link="true">dlib/image_loader/png_loader_abstract.h</spec_file>
         <description>        
            This object loads a Portable Network Graphics (PNG) image file into 
            an <a href="containers.html#array2d">array2d</a> of <a href="dlib/pixel.h.html">pixels</a>.
            <p>
               Note that you must define DLIB_PNG_SUPPORT if you want to use this object.  You
               must also set your build environment to link to the libpng library.  However,
               if you use CMake and dlib's default CMakeLists.txt file then it will get setup
               automatically.
            </p>
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>jpeg_loader</name>
         <file>dlib/image_io.h</file>
         <spec_file link="true">dlib/image_loader/jpeg_loader_abstract.h</spec_file>
         <description>        
            This object loads a JPEG image file into 
            an <a href="containers.html#array2d">array2d</a> of <a href="dlib/pixel.h.html">pixels</a>.
            <p>
               Note that you must define DLIB_JPEG_SUPPORT if you want to use this object.  You
               must also set your build environment to link to the libjpeg library.  However,
               if you use CMake and dlib's default CMakeLists.txt file then it will get setup
               automatically.
            </p>
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>load_dng</name>
         <file>dlib/image_io.h</file>
         <spec_file link="true">dlib/image_loader/image_loader_abstract.h</spec_file>
         <description>        
      This global function loads a dlib DNG file (a lossless compressed image format) into 
      an <a href="containers.html#array2d">array2d</a> of <a href="dlib/pixel.h.html">pixels</a>.
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>save_dng</name>
         <file>dlib/image_io.h</file>
         <spec_file link="true">dlib/image_saver/image_saver_abstract.h</spec_file>
         <description>        
      This global function writes an image out to an ostream as a dlib DNG file (a lossless 
      compressed image format). 
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>load_bmp</name>
         <file>dlib/image_io.h</file>
         <spec_file link="true">dlib/image_loader/image_loader_abstract.h</spec_file>
         <description>        
      This global function loads a MS Windows BMP file into an <a href="containers.html#array2d">array2d</a> of 
      <a href="dlib/pixel.h.html">pixels</a>.
         </description>

         <examples>
            <example>image_ex.cpp.html</example>
         </examples>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>save_bmp</name>
         <file>dlib/image_io.h</file>
         <spec_file link="true">dlib/image_saver/image_saver_abstract.h</spec_file>
         <description>        
      This global function writes an image out to an ostream as a MS Windows BMP file. 
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>draw_line</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/draw_abstract.h</spec_file>
         <description>        
            This global function draws a line onto an image.
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>assign_border_pixels</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/assign_image_abstract.h</spec_file>
         <description>        
            This global function assigns all the pixels in the border of an image to 
            a specific value.
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      
      <component>
         <name>assign_all_pixels</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/assign_image_abstract.h</spec_file>
         <description>        
            This global function assigns all the pixels in an image a specific value.
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>assign_image</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/assign_image_abstract.h</spec_file>
         <description>        
            This global function copies one image into another and performs any
            necessary color space conversions to make it work right. 
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>assign_image_scaled</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/assign_image_abstract.h</spec_file>
         <description>        
            This global function copies one image into another and performs any
            necessary color space conversions to make it work right.  Additionally,
            if the dynamic range of the source image is too big to fit into the destination image
            then it will attempt to perform the appropriate scaling.
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>get_histogram</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/equalize_histogram_abstract.h</spec_file>
         <description>        
            This global function computes an image's histogram and returns it in the
            form of a column or row <a href="containers.html#matrix">matrix</a> object.
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>edge_orientation</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/edge_detector_abstract.h</spec_file>
         <description>        
            This global function takes horizontal and vertical gradient magnitude
            values and returns the orientation of the gradient. 
         </description>
                                 
      </component>
            
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>equalize_histogram</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/equalize_histogram_abstract.h</spec_file>
         <description>        
            This global function performs histogram equalization on an image. 
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>hysteresis_threshold</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/thresholding_abstract.h</spec_file>
         <description>        
            This global function performs hysteresis thresholding on an image. 
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>sobel_edge_detector</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/edge_detector_abstract.h</spec_file>
         <description>        
            This global function performs spatial filtering on an image using the
            sobel edge detection filters.
         </description>
                                 
         <examples>
            <example>image_ex.cpp.html</example>
         </examples>
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>suppress_non_maximum_edges</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/edge_detector_abstract.h</spec_file>
         <description>        
            This global function performs non-maximum suppression on a gradient
            image.  
         </description>

         <examples>
            <example>image_ex.cpp.html</example>
         </examples>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>zero_border_pixels</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/assign_image_abstract.h</spec_file>
         <description>        
            This global function zeros the pixels on the border of an image.
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>spatially_filter_image</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/spatial_filtering_abstract.h</spec_file>
         <description>        
            This global function performs spatial filtering on an image with a user
            supplied filter.
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>pyramid_down</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/image_pyramid_abstract.h</spec_file>
         <description>        
               This is a simple function object to help create image pyramids.
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>auto_threshold_image</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/thresholding_abstract.h</spec_file>
         <description>        
            This global function performs a simple binary thresholding on an image with a user
            supplied threshold.  However, instead of taking a user supplied threshold
            it computes one from the image using k-means clustering.
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>threshold_image</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/thresholding_abstract.h</spec_file>
         <description>        
            This global function performs a simple binary thresholding on an image with a user
            supplied threshold.
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>binary_dilation</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/morphological_operations_abstract.h</spec_file>
         <description>        
            This global function performs the morphological operation of dilation on an image. 
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>binary_erosion</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/morphological_operations_abstract.h</spec_file>
         <description>        
            This global function performs the morphological operation of erosion on an image. 
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>binary_open</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/morphological_operations_abstract.h</spec_file>
         <description>        
            This global function performs a morphological opening on an image. 
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>binary_close</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/morphological_operations_abstract.h</spec_file>
         <description>        
            This global function performs a morphological closing on an image. 
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>binary_intersection</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/morphological_operations_abstract.h</spec_file>
         <description>        
            This global function computes the intersection of two binary images. 
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>binary_union</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/morphological_operations_abstract.h</spec_file>
         <description>        
            This global function computes the union of two binary images. 
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>binary_difference</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/morphological_operations_abstract.h</spec_file>
         <description>        
            This global function computes the difference of two binary images. 
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
      <component>
         <name>binary_complement</name>
         <file>dlib/image_transforms.h</file>
         <spec_file link="true">dlib/image_transforms/morphological_operations_abstract.h</spec_file>
         <description>        
            This global function computes the complement of a binary image. 
         </description>
                                 
      </component>
            
   <!-- ************************************************************************* -->
      
   </components>

   <!-- ************************************************************************* -->


</doc>

