From c09a8d90ea9f3ff83ed8ae99c21cc15bbc09f979 Mon Sep 17 00:00:00 2001
From: Arthur Moore <Arthur.Moore.git@cd-net.net>
Date: Tue, 23 Jun 2015 23:11:26 -0400
Subject: [PATCH] Added a function to split an image into multiple pieces.

This just preforms pointer manipulation.  The pieces are still part of the larger image.
---
 src/filters/filter_helper.cpp | 70 +++++++++++++++++++++++++++++++++++
 src/filters/filter_helper.hpp | 49 ++++++++++++------------
 2 files changed, 96 insertions(+), 23 deletions(-)
 create mode 100644 src/filters/filter_helper.cpp

diff --git a/src/filters/filter_helper.cpp b/src/filters/filter_helper.cpp
new file mode 100644
index 00000000..9dfc7df0
--- /dev/null
+++ b/src/filters/filter_helper.cpp
@@ -0,0 +1,70 @@
+#include "filter_helper.hpp"
+
+//Convert a 32 bit image to a 24 bit one
+void convert32To24(u32* src,u8* dst,unsigned int width, unsigned int height)
+{
+    //Need src as a single byte pointer for this to work
+    u8 * u8src = (u8*)src;
+
+    for(unsigned int y = 0; y < height ; y++)
+    {
+        for(unsigned int x = 0; x < width; x++)
+        {
+            //For each pixel copy r,g,b one byte at a time
+            for(unsigned int i = 0; i<3; i++)
+            {
+                *dst++ = *u8src++;
+            }
+            //Skip the alpha channel
+            u8src++;
+        }
+    }
+}
+
+//Get a pointer to the first pixel of a row inside an image
+u32 * GetVerticalOffset(u32 * image_pointer,unsigned int width,unsigned int vertical_offset,unsigned int scale=1)
+{
+    return image_pointer + (width * vertical_offset*scale*scale);
+}
+
+//Split an image into multiple sections, with each section being a certain number of rows of the original image
+std::vector<raw_image> splitImage(raw_image inImage, unsigned int number)
+{
+    std::vector<raw_image> outImages;
+    raw_image outImage;
+
+    //Handle if the user accidentally gave us a zero for number
+    if(number <= 0)
+    {
+        number = 1;
+    }
+
+    //The height of each image
+    unsigned int band_height = inImage.height/number;
+    //Don't let the last few rows get lost
+    unsigned int remainder_height = inImage.height%number;
+
+    //Start by setting the out pointer to the same as the in pointer
+    outImage.image = inImage.image;
+    //All images are the same width
+    outImage.width=inImage.width;
+    //All but the last are the same height
+    outImage.height=band_height;
+
+    //Process all but the last image
+    for(unsigned int i=0;i<(number-1);++i)
+    {
+        //Store the output image
+        outImages.push_back(outImage);
+        //Prepare for the next one (move the pointer band_height rows down)
+        outImage.image=outImage.image+(outImage.width*band_height);
+    }
+
+    //Process the last image (including the remainder)
+    outImage.height=band_height+remainder_height;
+    //Pointer manipulation was handled in the for loop
+    outImages.push_back(outImage);
+
+    //Give the user the results
+    return outImages;
+}
diff --git a/src/filters/filter_helper.hpp b/src/filters/filter_helper.hpp
index 726e2447..72bab7ec 100644
--- a/src/filters/filter_helper.hpp
+++ b/src/filters/filter_helper.hpp
@@ -3,6 +3,10 @@
 #ifndef FILTER_HELPER_HPP
 #define FILTER_HELPER_HPP
 
+#include <vector>
+
+#include <cstdint>
+typedef uint32_t u32;
 
 /**
     * Convert a 32 bit image to a 24 bit one
@@ -15,26 +19,7 @@
     * \param[in] width  The image width (in pixels)
     * \param[in] height The height width (in pixels)
     */
-inline void convert32To24(u32* src,u8* dst,unsigned int width, unsigned int height)
-{
-    //Need src as a single byte pointer for this to work
-    u8 * u8src = (u8*)src;
-
-    for(unsigned int y = 0; y < height ; y++)
-    {
-        for(unsigned int x = 0; x < width; x++)
-        {
-            //For each pixel copy r,g,b one byte at a time
-            for(unsigned int i = 0; i<3; i++)
-            {
-                *dst++ = *u8src++;
-            }
-            //Skip the alpha channel
-            u8src++;
-        }
-    }
-}
-
+void convert32To24(u32* src,u8* dst,unsigned int width, unsigned int height);
 /**
  * Get a pointer to the first pixel of a row inside an image
  *
@@ -46,9 +31,27 @@ inline void convert32To24(u32* src,u8* dst,unsigned int width, unsigned int heig
  * \param[in] scale             How much larger the output image will be
  * \return                      A pointer to the first pixel in the chosen row
  */
-inline u32 * GetVerticalOffset(u32 * image_pointer,unsigned int width,unsigned int vertical_offset,unsigned int scale=1)
+inline u32 * GetVerticalOffset(u32 * image_pointer,unsigned int width,unsigned int vertical_offset,unsigned int scale=1);
+
+/**
+ * A simple struct to keep track of an image pointer, and the image's size.
+ */
+struct raw_image
 {
-    return image_pointer + (width * vertical_offset*scale*scale);
-}
+    u32* image;
+    unsigned int width;
+    unsigned int height;
+};
+
+/**
+ * Split an image into multiple sections, with each section being a certain number of rows of the original image
+ *
+ * NOTE:  The returned images are not separate.  The pointers merely point to different parts of the original image.
+ *
+ * \param[in] inImage   The original image
+ * \param[in] number    The number of sections to split the image into
+ * \return              A vector containing the sections of the original image
+ */
+std::vector<raw_image> splitImage(raw_image inImage, unsigned int number);
 
 #endif //FILTER_HELPER_HPP