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.

.gitignore

@@ -91,4 +91,17 @@ Icon
 .AppleDesktop
 Network Trash Folder
 Temporary Items
-.apdisk
+.apdisk
+
+# Intellij
+.idea/
+*.iml
+
+
+###Snap###
+
+parts/
+prime/
+snap/
+stage/
+*.snap

README.md

@@ -13,14 +13,27 @@ For each 4x8 pixel cell of the (potentially downscaled) image:
 
 See the difference by disabling this optimization using the `-0` option. Or just take a look at the comparison image at the end of this text.
 
+## 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
 
+### Snap
+
+    sudo snap install --edge tiv
+
+### Build from source
+
     sudo apt install imagemagick || yum install ImageMagick
     git clone https://github.com/stefanhaustein/TerminalImageViewer.git
     cd TerminalImageViewer/src/main/cpp
     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)>
@@ -33,11 +46,14 @@ The shell will expand wildcards. By default, thumbnails and file names will be d
    https://build.opensuse.org/package/show/home:megamaced/terminalimageviewer
  - bperel has created a Docker image:
    https://hub.docker.com/r/bperel/terminalimageviewer
+ - teresaejunior has created a snapcraft.yaml file, which can build a Snap package with `sudo docker run -it --rm -v "$PWD:$PWD" -w "$PWD" snapcore/snapcraft sh -c 'apt-get update && snapcraft'`, and then installed with `sudo snap install --dangerous ./*.snap`.
 
 ## Common problems
 
  - If you see strange horizontal lines, the characters don't fully fill the character cell. Remove additional line spacing in your terminal app
  - Wrong colors? Try -256 to use a 256 color palette instead of 24 bit colors
+ - Strange characters? Try -0 or install an use full unicode font (e.g. inconsolata or firacode)
+ 
  
 ## Examples
 

snapcraft.yaml

@@ -0,0 +1,73 @@
+name: tiv
+version: "v1.0.0"
+summary: Terminal Image Viewer
+description: |
+  tiv is a small C++ program to display images in a (modern) terminal using
+  RGB ANSI codes and unicode block graphic characters.
+
+apps:
+  tiv:
+    command: usr/bin/tiv
+    plugs: [home]
+
+parts:
+  tiv:
+    plugin: make
+    source-type: tar
+    source: https://github.com/stefanhaustein/TerminalImageViewer/archive/v1.0.0.tar.gz
+    source-subdir: src/main/cpp
+    build-packages:
+      - g++
+      - make
+      - imagemagick
+    override-build: |
+      snapcraftctl build
+      mkdir -p $SNAPCRAFT_PART_INSTALL/usr/bin/
+      install $SNAPCRAFT_PART_BUILD/tiv $SNAPCRAFT_PART_INSTALL/usr/bin/
+  imagemagick:
+    plugin: autotools
+    source: https://www.imagemagick.org/download/releases/ImageMagick-7.0.8-23.tar.xz
+    source-type: tar
+    configflags:
+      - --enable-hdri=yes
+      - --enable-shared=yes
+      - --enable-static=yes
+      - --with-autotrace=yes
+      - --with-fpx=no
+      - --with-gnu-ld=yes
+      - --with-gslib=yes
+      - --with-modules=no
+      - --with-quantum-depth=32
+      - --with-rsvg=yes
+    build-packages:
+      - autoconf
+      - build-essential
+      - fftw-dev
+      - libautotrace-dev
+      - libbz2-dev
+      - libdjvulibre-dev
+      - libfftw3-dev
+      - libfontconfig1-dev
+      - libfreetype6-dev
+      - libgs-dev
+      - libgvc6
+      - libjbig-dev
+      - libjpeg-dev
+      - liblcms2-dev
+      - liblqr-1-0-dev
+      - libltdl-dev
+      - libmagick++-dev
+      - libopenexr-dev
+      - libopenjp2-7-dev
+      - libpango1.0-dev
+      - libperl-dev
+      - libpng12-dev
+      - librsvg2-dev
+      - libtiff5-dev
+      - libwebp-dev
+      - libwmf-dev
+      - libx11-dev
+      - lzma-dev
+      - ocl-icd-opencl-dev
+      - perlmagick
+      - zlib1g-dev

src/main/cpp/Makefile

@@ -1,15 +1,22 @@
-CXX=g++
+# set CXX to g++ if not set
+CXX ?= g++
 
-default: tiv
+# append necessary arguments
+override CPPFLAGS += -std=c++17 -Wall -fpermissive -fexceptions -O2
+override LDFLAGS  += -lstdc++fs -pthread -s
+
+all: tiv
 
 tiv.o: tiv.cpp CImg.h
-	$(CXX) -std=c++17  -Wall -fpermissive -fexceptions -O2 -c tiv.cpp -o tiv.o
+	$(CXX) $(CPPFLAGS) -c tiv.cpp -o $@
 
 tiv : tiv.o
-	$(CXX) tiv.o -o tiv -lstdc++fs -pthread -s
+	$(CXX) $^ -o $@ $(LDFLAGS)
 
-install: tiv
-	cp tiv /usr/local/bin/tiv
+.PHONY: all install clean
+install: all
+	test -d $(DESTDIR)/usr/local/bin || mkdir -p $(DESTDIR)/usr/local/bin
+	cp tiv $(DESTDIR)/usr/local/bin/tiv
 
 clean:
-	rm -f tiv tiv.o 
+	rm -f tiv tiv.o

src/main/cpp/tiv.cpp

@@ -195,8 +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;
   }
@@ -330,7 +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];
@@ -382,6 +381,31 @@ void emit_image(const cimg_library::CImg<unsigned char> & image, int flags) {
 }
 
 
+struct size {
+  size(unsigned int in_width, unsigned int in_height) :
+	width(in_width), height(in_height) {
+  }
+  size(cimg_library::CImg<unsigned int> img) :
+	width(img.width()), height(img.height()) {
+  }
+  unsigned int width;
+  unsigned int height;
+  size scaled(double scale) {
+    return size(width*scale, height*scale);
+  }
+  size fitted_within(size container) {
+    double scale = std::min(container.width / (double) width, container.height / (double) height);
+    return scaled(scale);
+  }
+};
+std::ostream& operator<<(std::ostream& stream, size sz) {
+  stream << sz.width << "x" << sz.height;
+  return stream;
+}
+
+
+
+
 void emit_usage() {
   std::cerr << "Terminal Image Viewer" << std::endl << std::endl;
   std::cerr << "usage: tiv [options] <image> [<image>...]" << std::endl << std::endl;
@@ -397,12 +421,42 @@ void emit_usage() {
 
 enum Mode {AUTO, THUMBNAILS, FULL_SIZE};
 
+
+/* Wrapper around CImg<T>(const char*) to ensure the result has 3 channels as RGB
+ */
+cimg_library::CImg<unsigned char> load_rgb_CImg(const char * const filename) {
+	cimg_library::CImg<unsigned char> image(filename);
+	if(image.spectrum() == 1) {
+		// Greyscale. Just copy greyscale data to all channels
+		cimg_library::CImg<unsigned char> rgb_image(image.width(), image.height(), image.depth(), 3);
+		for(unsigned int chn = 0; chn < 3; chn++) {
+			rgb_image.draw_image(0, 0, 0,chn, image);
+		}
+		return rgb_image;
+	}
+
+	return image;
+}
+
 int main(int argc, char* argv[]) {
+  int maxWidth = 80;
+  int maxHeight = 24;
+  bool sizeDetectionSuccessful = true;
   struct winsize w;
-  ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
-  
-  int maxWidth = w.ws_col * 4;
-  int maxHeight = w.ws_row * 8;
+  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 flags = 0;
   Mode mode = AUTO;
   int columns = 3;
@@ -452,14 +506,14 @@ int main(int argc, char* argv[]) {
   if (mode == FULL_SIZE || (mode == AUTO && file_names.size() == 1)) {
     for (unsigned int i = 0; i < file_names.size(); i++) {
       try {
-	cimg_library::CImg<unsigned char> image(file_names[i].c_str());
+	cimg_library::CImg<unsigned char> image = load_rgb_CImg(file_names[i].c_str());
       
 	if (image.width() > maxWidth || image.height() > maxHeight) {
-	  double scale = std::min(maxWidth / (double) image.width(), maxHeight / (double) image.height());
-	  image.resize((int) (image.width() * scale), (int) (image.height() * scale), -100, -100, 5);
+	  size new_size = size(image).fitted_within(size(maxWidth,maxHeight));
+	  image.resize(new_size.width, new_size.height, -100, -100, 5);
 	}
 	emit_image(image, flags);
-      } catch(cimg_library::CImgIOException e) {
+      } catch(cimg_library::CImgIOException & e) {
 	error = 1;
 	std::cerr << "File format is not recognized for '" << file_names[i] << "'" << std::endl;
       }
@@ -471,6 +525,7 @@ int main(int argc, char* argv[]) {
     int cw = (((maxWidth / 4) - 2 * (columns - 1)) / columns);
     int tw = cw * 4;
     cimg_library::CImg<unsigned char> image(tw * columns + 2 * 4 * (columns - 1), tw, 1, 3);
+    size maxThumbSize(tw, tw);
     
     while (index < file_names.size()) {
       image.fill(0);
@@ -479,21 +534,21 @@ int main(int argc, char* argv[]) {
       while (index < file_names.size() && count < columns) {
 	std::string name = file_names[index++];
 	try {
-	  cimg_library::CImg<unsigned char> original(name.c_str());
-	  unsigned int cut = name.find_last_of("/");
+	  cimg_library::CImg<unsigned char> original = load_rgb_CImg(name.c_str());
+	  auto cut = name.find_last_of("/");
 	  sb += cut == std::string::npos ? name : name.substr(cut + 1);
-	  int th = original.height() * tw / original.width();
-	  original.resize(tw, th, 1, -100, 5);
-	  image.draw_image(count * (tw + 8), (tw - th) / 2, 0, 0, original);
+	  size newSize = size(original).fitted_within(maxThumbSize);
+	  original.resize(newSize.width, newSize.height, 1, -100, 5);
+	  image.draw_image(count * (tw + 8) + (tw - newSize.width) / 2, (tw - newSize.height) / 2, 0, 0, original);
 	  count++;
 	  unsigned int sl = count * (cw + 2);
 	  sb.resize(sl - 2, ' ');
 	  sb += "  ";
-	} catch (std::exception e) {
+	} catch (std::exception & e) {
 	  // Probably no image; ignore.
 	}
       }
-      emit_image(image, flags);
+      if (count) emit_image(image, flags);
       std::cout << sb << std::endl << std::endl;
     }
   }