[freetype2] GSoC-2017-kushal a2e5fef 45/70: Comments in bitmap.c

[Kushal K S V S]

branch: GSoC-2017-kushal
commit a2e5fef55bec0a78f411cb7c857f8fd8e786b1a5
Author: Kushal K S V S <address@hidden>
Commit: Kushal K S V S <address@hidden>

    Comments in bitmap.c
---
 tests/make_png/bitmap.c | 570 +++++++++++++++++++++++++-----------------------
 1 file changed, 294 insertions(+), 276 deletions(-)

diff --git a/tests/make_png/bitmap.c b/tests/make_png/bitmap.c
index f006184..0f7278c 100644
--- a/tests/make_png/bitmap.c
+++ b/tests/make_png/bitmap.c
@@ -1,5 +1,8 @@
 #include "bitmap.h"
 
+/* Functions to generate MurmurHash3 values of the bitmap image */
+/*data with a constant as the seed */
+
 HASH_128 * Generate_Hash_x64_128( FT_Bitmap * bitmap, 
                                   HASH_128 * murmur)
 {    
@@ -12,7 +15,7 @@ HASH_128 * Generate_Hash_x64_128( FT_Bitmap * bitmap,
 
   return murmur;
 }
-
+/*Not used*/
 HASH_128 * Generate_Hash_x86_128( FT_Bitmap * bitmap,
                                   HASH_128 * murmur)
 {    
@@ -25,7 +28,7 @@ HASH_128 * Generate_Hash_x86_128( FT_Bitmap * bitmap,
 
   return murmur;
 }
-
+/*Not used*/
 HASH_32 * Generate_Hash_x86_32( FT_Bitmap * bitmap,
                                 HASH_32 * murmur)
 {    
@@ -39,117 +42,17 @@ HASH_32 * Generate_Hash_x86_32( FT_Bitmap * bitmap,
   return murmur;
 }
 
+/* This function takes in the IMAGE data and returns the pointer */
+/* to the pixel at co-ordinates (x,y). This is used to access the */
+/* pixel data */
+
 PIXEL * Pixel_At (IMAGE * bitmap, int x, int y)
 {
   return bitmap->pixels + bitmap->width * y + x;
 }
-    
-int Generate_PNG (IMAGE *bitmap,
-                  const char *path,
-                  int render_mode)
-{
-  FILE * fp;
-  png_structp png_ptr       = NULL;
-  png_infop info_ptr        = NULL;
-
-  size_t x, y;
-  png_byte ** row_pointers = NULL;
-
-  int status = -1;
-
-  int pixel_size = 4;
-  int depth = 8;
-  
-  fp = fopen (path, "wb");
-  if (! fp) {
-    goto fopen_failed;
-  }
-
-  png_ptr = png_create_write_struct ( PNG_LIBPNG_VER_STRING,
-                                      NULL,
-                                      NULL,
-                                      NULL);
-  if (png_ptr == NULL) {
-    goto png_create_write_struct_failed;
-  }
-  
-  info_ptr = png_create_info_struct (png_ptr);
-  if (info_ptr == NULL) {
-    goto png_create_info_struct_failed;
-  }
-
-  if (setjmp (png_jmpbuf (png_ptr))) {
-    goto png_failure;
-  }
-
-  png_set_IHDR (png_ptr,
-                info_ptr,
-                bitmap->width,
-                bitmap->height,
-                depth,
-                PNG_COLOR_TYPE_RGBA,
-                PNG_INTERLACE_NONE,
-                PNG_COMPRESSION_TYPE_DEFAULT,
-                PNG_FILTER_TYPE_DEFAULT);
-
-  row_pointers = png_malloc ( png_ptr,
-                              bitmap->height * sizeof (png_byte *));
 
-  for (y = 0; y < bitmap->height; y++) {
-
-    png_byte *row = 
-    png_malloc(png_ptr, sizeof(uint8_t) * bitmap->width * pixel_size);
-    row_pointers[y] = row;
-
-    for (x = 0; x < bitmap->width; x++) {
-
-      PIXEL * pixel = Pixel_At (bitmap, x, y);
-
-        if (render_mode == 3 || render_mode == 5)
-        {
-          *row++ = pixel->blue;
-          *row++ = pixel->green;
-          *row++ = pixel->red;
-          *row++ = pixel->alpha;
-          continue;
-        }
-
-        *row++ = pixel->red;
-        *row++ = pixel->green;
-        *row++ = pixel->blue;
-        *row++ = pixel->alpha;
-    }
-  }    
-
-  png_init_io ( png_ptr,
-                fp);
-
-  png_set_rows (png_ptr,
-                info_ptr,
-                row_pointers);
-
-  png_write_png ( png_ptr,
-                  info_ptr,
-                  PNG_TRANSFORM_IDENTITY,
-                  NULL);
-
-  status = 0;
-  
-  for (y = 0; y < bitmap->height; y++) {
-    png_free (png_ptr, row_pointers[y]);
-  }
-  png_free (png_ptr, row_pointers);
-  
-  free (bitmap->pixels);
-
-  png_failure:
-  png_create_info_struct_failed:
-    png_destroy_write_struct (&png_ptr, &info_ptr);
-  png_create_write_struct_failed:
-    fclose (fp);
-  fopen_failed:
-    return status;
-}
+/* Here we take the FT_Bitmap structure and make an IMAGE structure */
+/* with pixel data from the FT_Bitmap buffer */
 
 void Make_PNG(FT_Bitmap* bitmap,IMAGE* fruit,int i,int render_mode){
 
@@ -161,26 +64,29 @@ void Make_PNG(FT_Bitmap* bitmap,IMAGE* fruit,int i,int 
render_mode){
 
   switch(render_mode){
 
-    case 0 :  fruit->width = bitmap->width;           /* MONO and GRAY */
+    case 0 :  fruit->width = bitmap->width;           /* MONO */
               fruit->height  = bitmap->rows;
-
+              /* Allocate Memory to the IMAGE structure as per the */
+              /* dimensions of the FT_Bitmap image*/
               fruit->pixels = calloc ( fruit->width * fruit->height,
                                       sizeof (PIXEL));
 
               for (y = 0; y < fruit->height; y++) {
                 for (x = 0; x < fruit->width; x++) {
-
+                  /* Access pixel by co-ordinates */
                   PIXEL * pixel = Pixel_At ( fruit, x, y);
                   p = (y * bitmap->pitch ) + x;
 
                   value = bitmap->buffer[p];
-                  
+                  /* If there is some colour, make it white */
+                  /* else, make it black */
                   if ( value != 0x00 ){
                     value = 0xff;
                   }else{
                     value = 0x00;
                   }
-
+                  /* Invert the colours to make the background white*/
+                  /* and the character black */
                   pixel->red = 255- value;
                   pixel->green = 255- value;
                   pixel->blue = 255- value;
@@ -188,7 +94,7 @@ void Make_PNG(FT_Bitmap* bitmap,IMAGE* fruit,int i,int 
render_mode){
                 }
               }                    
               break;
-    case 1 :  fruit->width = bitmap->width;            /* MONO and GRAY */
+    case 1 :  fruit->width = bitmap->width;            /* GRAY */
               fruit->height  = bitmap->rows;
 
               fruit->pixels = calloc ( fruit->width * fruit->height,
@@ -200,8 +106,9 @@ void Make_PNG(FT_Bitmap* bitmap,IMAGE* fruit,int i,int 
render_mode){
                   PIXEL * pixel = Pixel_At ( fruit, x, y);
                   p = (y * bitmap->pitch ) + x;
 
+                  /* Access the image data from the buffer */
                   value = bitmap->buffer[p];
-                  
+                  /* R=G=B for Grayscale images */
                   pixel->red = 255- value;
                   pixel->green = 255- value;
                   pixel->blue = 255- value;
@@ -210,6 +117,12 @@ void Make_PNG(FT_Bitmap* bitmap,IMAGE* fruit,int i,int 
render_mode){
               }                    
               break;
 
+/********************************************************************/
+/* FT_Bitmap has 'width' three times the size of glyph in case of   */
+/* LCD rendering i.e. three adjacent values in bitmap buffer row    */
+/* correspond to one RGB triplet. Accessing the buffer accordingly  */
+/* and filling the RGB values of the IMAGE structure                */
+/********************************************************************/
     case 2 :
     case 3 :  fruit->width = bitmap->width / 3;        /* LCD */
               fruit->height  = bitmap->rows;
@@ -238,7 +151,12 @@ void Make_PNG(FT_Bitmap* bitmap,IMAGE* fruit,int i,int 
render_mode){
                 }
               }
               break;
-
+/********************************************************************/
+/* FT_Bitmap has 'height' three times the size of glyph in case of  */
+/* LCD_v rendering i.e. three adjacent values in bitmap buffer      */
+/* column correspond to one RGB triplet. Accessing the buffer       */
+/* accordingly and filling the RGB values of the IMAGE structure    */
+/********************************************************************/
     case 4 :
     case 5 :  fruit->width = bitmap->width;            /* LCD_V */
               fruit->height  = bitmap->rows / 3;
@@ -274,167 +192,123 @@ void Make_PNG(FT_Bitmap* bitmap,IMAGE* fruit,int i,int 
render_mode){
   }
 }
 
-void Read_PNG(char *filename, IMAGE * after_effect) {
-
-  int width, height, x, y;
-  png_bytep *row_pointers;
-
-  FILE *fp = fopen(filename, "rb");
-
-  png_structp png = png_create_read_struct( PNG_LIBPNG_VER_STRING, 
-                                            NULL, 
-                                            NULL, 
-                                            NULL);
-  if(!png) abort();
-
-  png_infop info = png_create_info_struct(png);
-  if(!info) abort();
-
-  if(setjmp(png_jmpbuf(png))) abort();
-
-  png_init_io(png, fp);
-
-  png_set_user_limits(png, 0x7fffffffL, 0x7fffffffL);
-
-  png_read_info(png, info);
+/********************************************************************/
+/* This function generates the PNG file taking the IMAGE structure  */
+/* , path to the file and the render_mode. ( Using libpng )         */
+/* 32-bit RGBA images are generated. Each channel is 8-bit with     */
+/* alpha channel set to 255. Transparency can be set accordingly    */
+/********************************************************************/
+int Generate_PNG (IMAGE *bitmap,
+                  const char *path,
+                  int render_mode)
+{
+  FILE * fp;
+  png_structp png_ptr       = NULL;
+  png_infop info_ptr        = NULL;
 
-  width      = png_get_image_width(png, info);
-  height     = png_get_image_height(png, info);
+  size_t x, y;
+  png_byte ** row_pointers = NULL;
 
-  after_effect->width = width;
-  after_effect->height = height;
+  int status = -1;
 
-  row_pointers = (png_bytep*)malloc(sizeof(png_bytep) * height);
-  for( y = 0; y < height; y++) {
-    row_pointers[y] = (png_byte*)malloc(png_get_rowbytes(png,info));
+  int pixel_size = 4; /* Each pixel is 4-byte */
+  int depth = 8; /* Each colour is 8-bit*/
+  
+  fp = fopen (path, "wb");
+  if (! fp) {
+    goto fopen_failed;
   }
 
-  png_read_image(png, row_pointers);
-
-  after_effect->pixels = 
-  (PIXEL*) malloc( width * height * sizeof(PIXEL));
-
-  for( y = 0; y < height; y++) {
-
-    png_bytep row = row_pointers[y];
-
-    for( x = 0; x < width; x++ ) {
-
-      png_bytep px = &(row[x * 4]);
-
-      PIXEL * pixel = Pixel_At ( after_effect, x, y);
-
-      pixel->red = px[0];
-      pixel->green = px[1];
-      pixel->blue = px[2];
-      pixel->alpha = px[3];
-    }
+  png_ptr = png_create_write_struct ( PNG_LIBPNG_VER_STRING,
+                                      NULL,
+                                      NULL,
+                                      NULL);
+  if (png_ptr == NULL) {
+    goto png_create_write_struct_failed;
+  }
+  
+  info_ptr = png_create_info_struct (png_ptr);
+  if (info_ptr == NULL) {
+    goto png_create_info_struct_failed;
   }
 
-  fclose(fp);
-}
-
-int Add_effect(IMAGE* base, IMAGE* test, IMAGE* out, int Effect_ID)
-{ 
-  int pixel_diff = 0;
-  int x,y;
+  if (setjmp (png_jmpbuf (png_ptr))) {
+    goto png_failure;
+  }
 
-  out->width = base->width;
-  out->height = base->height;
-  out->pixels = 
-  (PIXEL*)malloc(base->width * base->height * sizeof(PIXEL));
+  png_set_IHDR (png_ptr,
+                info_ptr,
+                bitmap->width,
+                bitmap->height,
+                depth,
+                PNG_COLOR_TYPE_RGBA,
+                PNG_INTERLACE_NONE,
+                PNG_COMPRESSION_TYPE_DEFAULT,
+                PNG_FILTER_TYPE_DEFAULT);
 
-  for( y = 0; y < base->height; y++) {
-    for( x = 0; x < base->width; x++ ) {
+  row_pointers = png_malloc ( png_ptr,
+                              bitmap->height * sizeof (png_byte *));
 
-      PIXEL * pixel_base = Pixel_At ( base, x, y);
-      PIXEL * pixel_test = Pixel_At ( test, x, y);
-      PIXEL * pixel_out = Pixel_At ( out, x, y);
+  for (y = 0; y < bitmap->height; y++) {
 
-      if (Effect_ID == 1)
-      {
-        if (pixel_base->red   == 255 &&
-            pixel_base->green == 255 &&
-            pixel_base->blue  == 255 &&
-            pixel_base->alpha == 255 )
-        {
-          pixel_out->red    = 255;
-          pixel_out->green  = 255;
-          pixel_out->blue   = 255;
-          pixel_out->alpha  = 255;
-        }else{
-          pixel_out->red    = 127;
-          pixel_out->green  = 127;
-          pixel_out->blue   = 127;
-          pixel_out->alpha  = 255;
-        }
-      }
+    png_byte *row = 
+    png_malloc(png_ptr, sizeof(uint8_t) * bitmap->width * pixel_size);
+    row_pointers[y] = row;
 
-      if (pixel_base->red   != pixel_test->red    ||
-          pixel_base->green != pixel_test->green  ||
-          pixel_base->blue  != pixel_test->blue   ||
-          pixel_base->alpha != pixel_test->alpha  )
-      {
-        pixel_out->red    = 255;
-        pixel_out->green  = 0;
-        pixel_out->blue   = 0;
-        pixel_out->alpha  = 255;
+    for (x = 0; x < bitmap->width; x++) {
 
-        pixel_diff++;
+      PIXEL * pixel = Pixel_At (bitmap, x, y);
 
-      }else{
-        if (Effect_ID == 2)
-        {
-          pixel_out->red    = pixel_base->red;
-          pixel_out->green  = pixel_base->green;
-          pixel_out->blue   = pixel_base->blue;
-          pixel_out->alpha  = pixel_base->alpha;
+        if (render_mode == 3 || render_mode == 5)
+        { /* For BGRA images */
+          *row++ = pixel->blue;
+          *row++ = pixel->green;
+          *row++ = pixel->red;
+          *row++ = pixel->alpha;
+          continue;
         }
-      }
+        /* For RGBA images */
+        *row++ = pixel->red;
+        *row++ = pixel->green;
+        *row++ = pixel->blue;
+        *row++ = pixel->alpha;
     }
-  }
-  return pixel_diff;
-}
-
-void Stitch(IMAGE* left, IMAGE* right, IMAGE* result){
-
-  int x, y;
+  }    
 
-  result->width = left->width + right->width;
-  result->height = MAX(left->height, right->height); 
+  png_init_io ( png_ptr,
+                fp);
 
-  result->pixels = 
-  (PIXEL*)calloc(result->width * result->height, sizeof(PIXEL));
+  png_set_rows (png_ptr,
+                info_ptr,
+                row_pointers);
 
-  for ( y = 0; y < left->height; ++y)
-  {
-    for ( x = 0; x < left->width; ++x)
-    {
-      PIXEL * pixel_left = Pixel_At ( left, x, y);
-      PIXEL * pixel_result = Pixel_At ( result, x, y);
+  png_write_png ( png_ptr,
+                  info_ptr,
+                  PNG_TRANSFORM_IDENTITY,
+                  NULL);
 
-      pixel_result->red    = pixel_left->red;
-      pixel_result->green  = pixel_left->green;
-      pixel_result->blue   = pixel_left->blue;
-      pixel_result->alpha  = pixel_left->alpha; 
-    }
+  status = 0;
+  
+  for (y = 0; y < bitmap->height; y++) {
+    png_free (png_ptr, row_pointers[y]);
   }
+  png_free (png_ptr, row_pointers);
+  
+  free (bitmap->pixels);
 
-  for ( y = 0; y < right->height; ++y)
-  {
-    for ( x = left->width; x < result->width; ++x)
-    {
-      PIXEL * pixel_right = Pixel_At ( right, x - left->width, y);
-      PIXEL * pixel_result = Pixel_At ( result, x, y);
-
-      pixel_result->red    = pixel_right->red;
-      pixel_result->green  = pixel_right->green;
-      pixel_result->blue   = pixel_right->blue;
-      pixel_result->alpha  = pixel_right->alpha; 
-    }
-  }
+  png_failure:
+  png_create_info_struct_failed:
+    png_destroy_write_struct (&png_ptr, &info_ptr);
+  png_create_write_struct_failed:
+    fclose (fp);
+  fopen_failed:
+    return status;
 }
 
+/********************************************************************/
+/* Compare the MurmurHash3 values ( x64_128 bit implemented )       */
+/* Returns 1 if they are different and 0 if identical.              */
+/********************************************************************/
 int Compare_Hash(HASH_128* hash_b, HASH_128* hash_t){
   if (hash_b->hash[0] != hash_t->hash[0] ||
       hash_b->hash[1] != hash_t->hash[1] ||
@@ -446,17 +320,11 @@ int Compare_Hash(HASH_128* hash_b, HASH_128* hash_t){
   return 0;
 }
 
-void Print_Row( FILE* fp, int index, char* name, int diff )
-{
-  fprintf(fp,
-    "<tr>\n\
-      <td>%04d</td>\n\
-      <td>%s</td>\n\
-      <td>%04d</td>\n\
-      <td id=\"image_row\"><img id=\"sprite\" src=\"images/%s.png\"></td>\n\
-    </tr>\n", index, name, diff, name);
-}
-
+/********************************************************************/
+/* Returns the index of the first-column to have a coloured pixel.  */
+/* 'Coloured' means the pixel isn't in the background               */
+/* Background Colour RGB = ( 255,255,255 )                          */
+/********************************************************************/
 int First_Column(IMAGE* input){
 
   int x, y;
@@ -481,6 +349,7 @@ int First_Column(IMAGE* input){
   return input->width;
 }
 
+/* Returns the index of the first-row to have a coloured pixel. */
 int First_Row(IMAGE* input){
 
   int x, y;
@@ -505,8 +374,16 @@ int First_Row(IMAGE* input){
   return input->height;
 }
 
+/********************************************************************/
+/* The following two  functions takes two IMAGES with different     */
+/* dimensions and aligns the two images based on the first pixel    */
+/* that isn't in the background i.e. RGB != ( 255,255,255 ).        */
+/* The first argument is the one which has smaller height/width.    */
+/* Columns/Rows are appended to the smaller image to match the      */
+/* dimensions.                                                      */
+/********************************************************************/
 IMAGE* Append_Columns(IMAGE* small, IMAGE* big){
-  
+  /* small->width < big->width */
   int x, y;
 
   IMAGE* result = (IMAGE*)malloc(sizeof(IMAGE));
@@ -518,12 +395,12 @@ IMAGE* Append_Columns(IMAGE* small, IMAGE* big){
 
   int first_col = First_Column(big);
 
-  for ( x = 0; x < first_col; ++x)
+  for ( x = 0; x < first_col; ++x) /* Filling White columns */
   {
     for ( y = 0; y < result->height; ++y)
     {
       PIXEL * pixel_result = Pixel_At ( result, x, y);
-
+      /* Filling White columns */
       pixel_result->red    = 255;
       pixel_result->green  = 255;
       pixel_result->blue   = 255;
@@ -531,13 +408,13 @@ IMAGE* Append_Columns(IMAGE* small, IMAGE* big){
     }
   }
 
-  for ( y = 0; y < result->height; ++y)
+  for ( y = 0; y < result->height; ++y) 
   {
     for ( x = first_col; x < first_col + small->width; ++x)
     {
       PIXEL * pixel_small = Pixel_At ( small, (x - first_col), y);
       PIXEL * pixel_result = Pixel_At ( result, x, y);
-
+      /* Putting the original IMAGE data */
       pixel_result->red    = pixel_small->red;
       pixel_result->green  = pixel_small->green;
       pixel_result->blue   = pixel_small->blue;
@@ -550,7 +427,7 @@ IMAGE* Append_Columns(IMAGE* small, IMAGE* big){
     for ( y = 0; y < result->height; ++y)
     {
       PIXEL * pixel_result = Pixel_At ( result, x, y);
-
+      /* Filling White columns */
       pixel_result->red    = 255;
       pixel_result->green  = 255;
       pixel_result->blue   = 255;
@@ -562,7 +439,7 @@ IMAGE* Append_Columns(IMAGE* small, IMAGE* big){
 }
 
 IMAGE* Append_Rows(IMAGE* small, IMAGE* big){
-  
+  /* small->height < big->height */
   int x, y;
 
   IMAGE* result = (IMAGE*)malloc(sizeof(IMAGE));
@@ -576,10 +453,10 @@ IMAGE* Append_Rows(IMAGE* small, IMAGE* big){
 
   for ( y = 0; y < first_row; ++y)
   {
-    for ( x = 0; x < result->width; ++x)
+    for ( x = 0; x < result->width; ++x) 
     {
       PIXEL * pixel_result = Pixel_At ( result, x, y);
-
+      /* Filling White rows */
       pixel_result->red    = 255;
       pixel_result->green  = 255;
       pixel_result->blue   = 255;
@@ -590,10 +467,10 @@ IMAGE* Append_Rows(IMAGE* small, IMAGE* big){
   for ( y = first_row; y < first_row + small->height; ++y)
   {
     for ( x = 0; x < result->width; ++x)
-    {
+    { 
       PIXEL * pixel_small = Pixel_At ( small, x, y - first_row);
       PIXEL * pixel_result = Pixel_At ( result, x, y);
-
+      /* Putting the original IMAGE data */
       pixel_result->red    = pixel_small->red;
       pixel_result->green  = pixel_small->green;
       pixel_result->blue   = pixel_small->blue;
@@ -606,7 +483,7 @@ IMAGE* Append_Rows(IMAGE* small, IMAGE* big){
     for ( x = 0; x < result->width; ++x)
     {
       PIXEL * pixel_result = Pixel_At ( result, x, y);
-
+      /* Filling White rows */
       pixel_result->red    = 255;
       pixel_result->green  = 255;
       pixel_result->blue   = 255;
@@ -617,6 +494,146 @@ IMAGE* Append_Rows(IMAGE* small, IMAGE* big){
   return result; 
 }
 
+/********************************************************************/
+/* This fuction visually highlights the differences between the two */
+/* images generated for the same glyph. There are two effects each  */
+/* given an Effect_ID.                                              */
+/* This function generates a new IMAGE structure after comparing and*/
+/* adding the desired effect.                                       */
+/*                                                                  */
+/* Effect_ID =1 means that the differences in pixels are highlighted*/
+/* and the pixels that are same are in GRAY (RGB = (128,128,128))   */
+/*                                                                  */
+/* Effect_ID =2 means that the differences in pixels are highlighted*/
+/* over the 'base' version's rendered image                         */
+/*                                                                  */
+/* Highlighting is done in RED colour i.e. RGB=( 255, 0, 0) for     */
+/* mono, grayscale and RGB-LCD displays and for BGR-LCD displays    */
+/* is is done in BLUE colour i.e. RGB = ( 0, 0, 255).               */
+/********************************************************************/
+int Add_effect(IMAGE* base, IMAGE* test, IMAGE* out, int Effect_ID)
+{ 
+  int pixel_diff = 0;
+  int x,y;
+  /* new IMAGE */
+  out->width = base->width;
+  out->height = base->height;
+  out->pixels = 
+  (PIXEL*)malloc(base->width * base->height * sizeof(PIXEL));
+
+  for( y = 0; y < base->height; y++) {
+    for( x = 0; x < base->width; x++ ) {
+
+      PIXEL * pixel_base = Pixel_At ( base, x, y);
+      PIXEL * pixel_test = Pixel_At ( test, x, y);
+      PIXEL * pixel_out = Pixel_At ( out, x, y);
+
+      if (Effect_ID == 1)
+      { /* If colour is white */
+        if (pixel_base->red   == 255 &&
+            pixel_base->green == 255 &&
+            pixel_base->blue  == 255 &&
+            pixel_base->alpha == 255 )
+        {
+          pixel_out->red    = 255; /* White*/
+          pixel_out->green  = 255;
+          pixel_out->blue   = 255;
+          pixel_out->alpha  = 255;
+        }else{
+          pixel_out->red    = 127; /* Gray */
+          pixel_out->green  = 127;
+          pixel_out->blue   = 127;
+          pixel_out->alpha  = 255;
+        }
+      }
+      /* if colour is different*/
+      if (pixel_base->red   != pixel_test->red    ||
+          pixel_base->green != pixel_test->green  ||
+          pixel_base->blue  != pixel_test->blue   ||
+          pixel_base->alpha != pixel_test->alpha  )
+      { /* Highlighting pixels */
+        pixel_out->red    = 255; 
+        pixel_out->green  = 0;
+        pixel_out->blue   = 0;
+        pixel_out->alpha  = 255;
+
+        pixel_diff++;
+
+      }else{
+        if (Effect_ID == 2)
+        {
+          pixel_out->red    = pixel_base->red;
+          pixel_out->green  = pixel_base->green;
+          pixel_out->blue   = pixel_base->blue;
+          pixel_out->alpha  = pixel_base->alpha;
+        }
+      }
+    }
+  }
+  return pixel_diff;
+}
+
+/********************************************************************/
+/* This function takes two IMAGE structures and stitches the images */
+/* horizontally to make one IMAGE.                                  */
+/* i.e. ( result->width =  left->width + right->width )             */
+/* The first argument forms the left part of the image and the      */
+/* second forms the right part.                                     */
+/* This returns the pointer to the stitched image                   */
+/********************************************************************/
+
+void Stitch(IMAGE* left, IMAGE* right, IMAGE* result){
+
+  int x, y;
+
+  result->width = left->width + right->width;
+  result->height = MAX(left->height, right->height); 
+
+  result->pixels = 
+  (PIXEL*)calloc(result->width * result->height, sizeof(PIXEL));
+
+  for ( y = 0; y < left->height; ++y)
+  {
+    for ( x = 0; x < left->width; ++x)
+    {
+      PIXEL * pixel_left = Pixel_At ( left, x, y);
+      PIXEL * pixel_result = Pixel_At ( result, x, y);
+      /* Filling Left part of the image*/
+      pixel_result->red    = pixel_left->red;
+      pixel_result->green  = pixel_left->green;
+      pixel_result->blue   = pixel_left->blue;
+      pixel_result->alpha  = pixel_left->alpha; 
+    }
+  }
+
+  for ( y = 0; y < right->height; ++y)
+  {
+    for ( x = left->width; x < result->width; ++x)
+    {
+      PIXEL * pixel_right = Pixel_At ( right, x - left->width, y);
+      PIXEL * pixel_result = Pixel_At ( result, x, y);
+      /* Filling right part of the image*/
+      pixel_result->red    = pixel_right->red;
+      pixel_result->green  = pixel_right->green;
+      pixel_result->blue   = pixel_right->blue;
+      pixel_result->alpha  = pixel_right->alpha; 
+    }
+  }
+}
+
+/* This prints a row to the HTML file for the list-view page. */
+void Print_Row( FILE* fp, int index, char* name, int diff )
+{
+  fprintf(fp,
+    "<tr>\n\
+      <td>%04d</td>\n\
+      <td>%s</td>\n\
+      <td>%04d</td>\n\
+      <td id=\"image_row\"><img id=\"sprite\" src=\"images/%s.png\"></td>\n\
+    </tr>\n", index, name, diff, name);
+}
+
+/* To calculate the Difference-Metric used in the list-view page */
 int Image_Diff( IMAGE* base, IMAGE* test){
 
   int diff = 0;
@@ -632,3 +649,4 @@ int Image_Diff( IMAGE* base, IMAGE* test){
 
   return diff;
 }
+/* For more information on the list-view page, go to README */