Make it possible to partially specify the geometry.

Issues #66 #64

README.md

@@ -67,7 +67,10 @@ grid uses `--grid=2` and is pixelated with `-pq`).
 ```
 usage: timg [options] <image/video> [<image/video>...]
 Options:
-        -g<w>x<h>      : Output geometry in character cells. Terminal is 160x50
+        -g<w>x<h>      : Output geometry in character cells. Partial geometry
+                         leaving out one value -g<w>x or -gx<h> is possible,
+                         the other value it then derived from the terminal size.
+                         Default derived from terminal size is 160x50
         -p<pixelation> : Pixelation: 'h' = half blocks    'q' = quarter blocks
                                      'k' = kitty graphics 'i' = iTerm2 graphics
                          Default: Auto-detect graphics, otherwise 'quarter'.

man/timg.1

@@ -1,4 +1,4 @@
-.\" Automatically generated by Pandoc 2.9.2.1
+.\" Automatically generated by Pandoc 2.13
 .\"
 .TH "timg" "1" "Feb 2021" "" ""
 .hy
@@ -52,6 +52,12 @@ By default, the size is determined by the available space in the
 terminal.
 The image is scaled to fit inside the available box to fill the screen;
 see \f[B]-W\f[R] if you want to fill the width.
+.RS
+.PP
+It is possible to only partially specify the size before or after the
+\f[B]x\f[R] separator, like \f[B]-gx\f[R] or \f[B]-gx\f[R].
+The corresponding other value is then derived from the terminal size.
+.RE
 .TP
 \f[B]-p\f[R] \f[I]<[h|q|k|i]>\f[R], \f[B]--pixelation\f[R]=\f[I][h|q|k|i]\f[R]
 Choice for pixelation of the content.

man/timg.1.md

@@ -42,11 +42,15 @@ these file decoders (GraphicsMagick or libav respectively).
 
 ## General Options
 **-g** *<width>x<height>*
-:     Output image to fit inside given geometry. By default, the size is
+:    Output image to fit inside given geometry. By default, the size is
      determined by the available space in the terminal. The image is
      scaled to fit inside the available box to fill the screen; see **-W** if
      you want to fill the width.
 
+     It is possible to only partially specify the size before or after the
+     **x** separator, like **-g<width>x** or **-gx<height>**. The corresponding
+     other value is then derived from the terminal size.
+
 **-p** *&lt;[h|q|k|i]&gt;*, **-\-pixelation**=*[h|q|k|i]*
 :    Choice for pixelation of the content. Value 'h' chooses unicode half
      block characters, while 'q' chooses quarter blocks.

src/timg.cc

@@ -154,7 +154,10 @@ static int usage(const char *progname, ExitCode exit_code,
     fprintf(stderr, "usage: %s [options] <%s> [<%s>...]\n", progname,
             kFileType, kFileType);
     fprintf(stderr, "\e[1mOptions\e[0m:\n"
-            "\t-g<w>x<h>      : Output geometry in character cells. Terminal is %dx%d\n"
+            "\t-g<w>x<h>      : Output geometry in character cells. Partial geometry\n"
+            "\t                 leaving out one value -g<w>x or -gx<h> is possible,\n"
+            "\t                 the other value it then derived from the terminal size.\n"
+            "\t                 Default derived from terminal size is %dx%d\n"
             "\t-p<pixelation> : Pixelation: 'h' = half blocks    'q' = quarter blocks\n"
             "\t                             'k' = kitty graphics 'i' = iTerm2 graphics\n"
             "\t                 Default: Auto-detect graphics, otherwise 'quarter'.\n"
@@ -393,8 +396,10 @@ int main(int argc, char *argv[]) {
                               long_options, &option_index))!=-1) {
         switch (opt) {
         case 'g':
-            if (sscanf(optarg, "%dx%d",
-                       &geometry_width, &geometry_height) < 2) {
+            // Parse xHEIGHT, WIDTHx, WIDTHxHEIGHT
+            if ((sscanf(optarg, "x%d", &geometry_height) == 0) &&
+                (sscanf(optarg, "%dx%d",
+                        &geometry_width, &geometry_height) < 1)) {
                 fprintf(stderr, "Invalid size spec '%s'", optarg);
                 return usage(argv[0], ExitCode::kParameterError,
                              geometry_width, geometry_height);
@@ -812,6 +817,8 @@ int main(int argc, char *argv[]) {
     if (verbose) {
         fprintf(stderr, "Terminal cells: %dx%d  cell-pixels: %dx%d\n",
                 term.cols, term.rows, term.font_width_px, term.font_height_px);
+        fprintf(stderr, "Active Geometry: %dx%d\n",
+                geometry_width, geometry_height);
         const Duration d = end_show - start_show;
         const uint64_t written_bytes =
             sequencer.bytes_total() - sequencer.bytes_skipped();