output redirection and color calculation fixes; minor improvements

fix: no longer accessing unexisting element of color_per_count;
fix: improved redirection handing;
fix: don't print empty rows in thumbs mode.

README.md

@@ -15,6 +15,7 @@ See the difference by disabling this optimization using the `-0` option. Or just
 
 ## News
 
+- 2019-03-26: Exciting week: @Cableo has fixed output redirection, @boretom has added cross-compilation support to the build file and @AlanDeSmet has fixed tall thumbnails and greyscale images.
 - 2019-01-14: Install via snap: `sudo snap install --edge tiv`
 
 ## Installation
@@ -31,6 +32,8 @@ See the difference by disabling this optimization using the `-0` option. Or just
     make
     sudo make install
 
+Note: On MacOS, you'll need to install GCC because of this issue: https://stackoverflow.com/q/42633477. Find some more details here: https://github.com/stefanhaustein/TerminalImageViewer/issues/36
+
 ## Usage
 
     tiv [options] <filename(s)>
@@ -66,8 +69,3 @@ The top image was generated with the character optimization disabled via the `-0
 
 ![Comparison](https://i.imgur.com/OzdCeh6.png)
 
-## Save file 
-
-Saving the disk image for use in other processes or softwares via the -o option
-
-![Persistence](https://i.imgur.com/LMb5KBX.png)

src/main/cpp/tiv.cpp

@@ -17,7 +17,6 @@ const int FLAG_BG = 2;
 const int FLAG_MODE_256 = 4;
 const int FLAG_24BIT = 8;
 const int FLAG_NOOPT = 16;
-const int FLAG_SAVE  = 32;
 
 const int COLOR_STEP_COUNT = 6;
 const int COLOR_STEPS[COLOR_STEP_COUNT] = {0, 0x5f, 0x87, 0xaf, 0xd7, 0xff};
@@ -196,8 +195,7 @@ CharData getCharData(const cimg_library::CImg<unsigned char> & image, int x0, in
   int count2 = iter->first;
   long max_count_color_1 = iter->second;
   long max_count_color_2 = max_count_color_1;
-  if (iter != color_per_count.rend()) {
-    ++iter;
+  if ((++iter) != color_per_count.rend()) {
     count2 += iter->first;
     max_count_color_2 = iter->second;
   }
@@ -331,7 +329,7 @@ void emit_color(int flags, int r, int g, int b) {
   int gq = COLOR_STEPS[gi];
   int bq = COLOR_STEPS[bi];
   
-  int gray = std::round(r * 0.2989f + g * 0.5870f + b * 0.1140f);
+  int gray = static_cast<int>(std::round(r * 0.2989f + g * 0.5870f + b * 0.1140f));
 
   int gri = best_index(gray, GRAYSCALE_STEPS, GRAYSCALE_STEP_COUNT);
   int grq = GRAYSCALE_STEPS[gri];
@@ -419,7 +417,6 @@ void emit_usage() {
   std::cerr << "  -help     : Display this help text." << std::endl;
   std::cerr << "  -h <num>  : Set the maximum height to <num> lines." << std::endl;
   std::cerr << "  -w <num>  : Set the maximum width to <num> characters." << std::endl << std::endl;
-  std::cerr << "  -o <name> : Output file name." << std::endl << std::endl;
 }
 
 enum Mode {AUTO, THUMBNAILS, FULL_SIZE};
@@ -442,20 +439,27 @@ cimg_library::CImg<unsigned char> load_rgb_CImg(const char * const filename) {
 }
 
 int main(int argc, char* argv[]) {
+  int maxWidth = 80;
+  int maxHeight = 24;
+  bool sizeDetectionSuccessful = true;
   struct winsize w;
-  ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
-
-  //If redirect STDOUT to one file ( col and row == 0 )
-  if(w.ws_col == 0 && w.ws_row == 0) {
-    ioctl(0, TIOCGWINSZ, &w);
+  int ioStatus = ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
+  // If redirecting STDOUT to one file ( col or row == 0, or the previous ioctl call's failed )
+  if (ioStatus != 0 || (w.ws_col | w.ws_row) == 0) {
+    ioStatus = ioctl(STDIN_FILENO, TIOCGWINSZ, &w);
+    if (ioStatus != 0 || (w.ws_col | w.ws_row) == 0) {
+      std::cerr << "Warning: failed to determine most reasonable size, defaulting to 80x24" << std::endl;
+       sizeDetectionSuccessful = false;
+    }
+  }
+  if (sizeDetectionSuccessful)
+  {
+    maxWidth = w.ws_col * 4;
+    maxHeight = w.ws_row * 8;
   }
-
-  int maxWidth = w.ws_col * 4;
-  int maxHeight = w.ws_row * 8;
   int flags = 0;
   Mode mode = AUTO;
   int columns = 3;
-  std::string output_file;  
 
   std::vector<std::string> file_names;
   int error = 0;
@@ -469,9 +473,6 @@ int main(int argc, char* argv[]) {
     std::string arg(argv[i]);
     if (arg == "-0") {
       flags |= FLAG_NOOPT;
-    } else if (arg == "-o") {
-      output_file = argv[++i];
-      flags |= FLAG_SAVE;
     } else if (arg == "-c") {
       columns = std::stoi(argv[++i]);
     } else if (arg == "-d") {
@@ -501,9 +502,7 @@ int main(int argc, char* argv[]) {
     }
   }
 
-  if ((flags & FLAG_SAVE) != 0) {
-    freopen(output_file.c_str(),"w",stdout); 	  
-  }	
+
   if (mode == FULL_SIZE || (mode == AUTO && file_names.size() == 1)) {
     for (unsigned int i = 0; i < file_names.size(); i++) {
       try {
@@ -536,7 +535,7 @@ int main(int argc, char* argv[]) {
 	std::string name = file_names[index++];
 	try {
 	  cimg_library::CImg<unsigned char> original = load_rgb_CImg(name.c_str());
-	  unsigned int cut = name.find_last_of("/");
+	  auto cut = name.find_last_of("/");
 	  sb += cut == std::string::npos ? name : name.substr(cut + 1);
 	  size newSize = size(original).fitted_within(maxThumbSize);
 	  original.resize(newSize.width, newSize.height, 1, -100, 5);
@@ -549,7 +548,7 @@ int main(int argc, char* argv[]) {
 	  // Probably no image; ignore.
 	}
       }
-      emit_image(image, flags);
+      if (count) emit_image(image, flags);
       std::cout << sb << std::endl << std::endl;
     }
   }