start histogram, fix image orientation

lib/histogram.h

@@ -0,0 +1,94 @@
+#include <cstdint>
+#include "./imgui.h"
+#include "./imgui_internal.h"
+
+class Histogram {
+
+public:
+  unsigned int **counts = nullptr;
+  int width = 0;
+  int height = 0;
+  int channels = 0;
+
+  Histogram(); 
+
+  void Load() {
+
+  };
+
+  void Draw() {
+
+  };
+  
+};
+
+inline void histogram(const int width, const int height, const int channels, const unsigned char* const bits) {
+  unsigned int count[4][256] = {0};
+
+  const unsigned char* ptrCols = bits;
+
+  ImGui::InvisibleButton("histogram", ImVec2(512, 256));
+  for (int l = 0; l < height * width; l++)
+  {
+    count[0][*ptrCols++]++;
+    count[1][*ptrCols++]++;
+    count[2][*ptrCols++]++;
+    count[3][*ptrCols++]++;
+  }
+
+  unsigned int maxv = count[0][0];
+  unsigned int* pCount = &count[0][0];
+  for (int i = 0; i < 3 * 256; i++, pCount++)
+  {
+    maxv = (maxv > *pCount) ? maxv : *pCount;
+  }
+
+  ImDrawList* drawList = ImGui::GetWindowDrawList();
+  const ImVec2 rmin = ImGui::GetItemRectMin();
+  const ImVec2 rmax = ImGui::GetItemRectMax();
+  const ImVec2 size = ImGui::GetItemRectSize();
+  const float hFactor = size.y / float(maxv);
+
+  for (int i = 0; i <= 10; i++)
+  {
+    float ax = rmin.x + (size.x / 10.f) * float(i);
+    float ay = rmin.y + (size.y / 10.f) * float(i);
+    drawList->AddLine(ImVec2(rmin.x, ay), ImVec2(rmax.x, ay), 0x80808080);
+    drawList->AddLine(ImVec2(ax, rmin.y), ImVec2(ax, rmax.y), 0x80808080);
+  }
+
+  const float barWidth = (size.x / 256.f);
+  for (int j = 0; j < 256; j++)
+  {
+    // pixel count << 2 + color index(on 2 bits)
+    uint32_t cols[3] = {(count[0][j] << 2), (count[1][j] << 2) + 1, (count[2][j] << 2) + 2};
+    if (cols[0] > cols[1])
+      ImSwap(cols[0], cols[1]);
+    if (cols[1] > cols[2])
+      ImSwap(cols[1], cols[2]);
+    if (cols[0] > cols[1])
+      ImSwap(cols[0], cols[1]);
+    float heights[3];
+    uint32_t colors[3];
+    uint32_t currentColor = 0xFFFFFFFF;
+    for (int i = 0; i < 3; i++)
+    {
+      heights[i] = rmax.y - (cols[i] >> 2) * hFactor;
+      colors[i] = currentColor;
+      currentColor -= 0xFF << ((cols[i] & 3) * 8);
+    }
+
+    float currentHeight = rmax.y;
+    const float left = rmin.x + barWidth * float(j);
+    const float right = left + barWidth;
+    for (int i = 0; i < 3; i++)
+    {
+      if (heights[i] >= currentHeight)
+      {
+        continue;
+      }
+      drawList->AddRectFilled(ImVec2(left, currentHeight), ImVec2(right, heights[i]), colors[i]);
+      currentHeight = heights[i];
+    }
+  }
+}

main.cpp

@@ -37,6 +37,8 @@
 
 #include <exiv2/exiv2.hpp>
 
+#include "lib/histogram.h"
+
 struct Args : public argparse::Args {
   std::string &fpath = arg("path to the image");
 };
@@ -228,8 +230,6 @@ Texture LoadTexture(const char * path)
 
     auto exif = printExifData(path);
 
-
-
     GLenum dataFormat = GL_RGBA;
     GLuint textureHandle;
     glGenTextures(1, &textureHandle);
@@ -244,6 +244,23 @@ Texture LoadTexture(const char * path)
     t.channels = channelCount;
     t.exif = exif;
 
+    if (t.exif.ImageOrientation == "3") {
+      RotateImage(t);
+      ReloadTexture(t, t.size.x, t.size.y);
+      t = ReloadTexture(t, t.size.y, t.size.x);
+      RotateImage(t);
+      t = ReloadTexture(t, t.size.y, t.size.x);
+    } else if (t.exif.ImageOrientation == "6") {
+      RotateImage(t);
+      t = ReloadTexture(t, t.size.y, t.size.x);
+    } else if (t.exif.ImageOrientation == "8") {
+      RotateImage(t);
+      t = ReloadTexture(t, t.size.y, t.size.x);
+      RotateImage(t);
+      t = ReloadTexture(t, t.size.y, t.size.x);
+      RotateImage(t);
+      t = ReloadTexture(t, t.size.y, t.size.x);
+    }
 
     return t;
 }
@@ -596,6 +613,12 @@ int main(int argc, char* argv[]) {
           ImGui::TableSetColumnIndex(1);
           ImGui::Text("%sx%s", t.exif.ImageDimensionX.c_str(), t.exif.ImageDimensiony.c_str());
 
+          ImGui::TableNextRow();
+          ImGui::TableSetColumnIndex(0);
+          ImGui::Text("Orientation");
+          ImGui::TableSetColumnIndex(1);
+          ImGui::Text("%s", t.exif.ImageOrientation.c_str());
+
           ImGui::EndTable();
         }