Merge pull request #52 from mdesantis/preserve-aspect-ratio

Preserve aspect ratio during resizing when the user provides both width and height

docs/imgcat.1

@@ -1,6 +1,6 @@
 .\" Automatically generated by Pandoc 2.9.2.1
 .\"
-.TH "IMGCAT" "1" "October 31, 2023" "imgcat User Manual" "meow"
+.TH "IMGCAT" "1" "December 10, 2023" "imgcat User Manual" "meow"
 .hy
 .SH NAME
 .PP
@@ -26,8 +26,8 @@ This can be overridden using \f[B]-w\f[R] to adjust the maximum width or
 the terminal; and \f[B]-d\f[R] to explicitly set the color depth.
 You may also use \f[B]-r\f[R] to adjust the height (\[lq]r\[rq] for
 \[lq]number of rows\[rq]).
-If only one of \f[B]-w\f[R] or \f[B]-r\f[R] is provided, the image will
-be scaled without affecting the aspect ratio, if possible.
+The image will be scaled without affecting the aspect ratio, unless
+\f[B]-P\f[R] is provided.
 .PP
 Setting \f[B]-H\f[R] enables the use of half-height block drawing
 characters (as opposed to \[lq]full height\[rq] spaces used in the
@@ -76,6 +76,9 @@ Does nothing if \f[B]\[en]no-resize\f[R] is provided.
 Maintains the original image\[cq]s aspect ratio if \f[B]\[en]width\f[R]
 is NOT provided.
 .TP
+\f[B]-P\f[R], \f[B]\[en]no-preserve-aspect-ratio\f[R]
+Does not preserve aspect ratio during image resizing.
+.TP
 \f[B]-R\f[R], \f[B]\[en]no-resize\f[R]
 Does not resize the image to fit the terminal\[cq]s width.
 Overrides both \f[B]\[en]width\f[R] and \f[B]\[en]height\f[R].

docs/imgcat.1.md

@@ -21,8 +21,8 @@ detected for your terminal. This can be overridden using **-w** to
 adjust the maximum width or **-R** to prevent resizing, even if the
 image is too big to fit in the terminal; and **-d** to explicitly set
 the color depth. You may also use **-r** to adjust the height ("r" for
-"number of rows"). If only one of **-w** or **-r** is provided, the
-image will be scaled without affecting the aspect ratio, if possible.
+"number of rows"). The image will be scaled without affecting the aspect
+ratio, unless **-P** is provided.
 
 Setting **-H** enables the use of half-height block drawing characters
 (as opposed to "full height" spaces used in the default mode). This
@@ -69,6 +69,9 @@ you're having a problem with this.
   Does nothing if **--no-resize** is provided. Maintains the original image's
   aspect ratio if **--width** is NOT provided.
 
+**-P**, **--no-preserve-aspect-ratio**
+  ~ Does not preserve aspect ratio during image resizing.
+
 **-R**, **--no-resize**
   ~ Does not resize the image to fit the terminal's width. Overrides
   both **--width** and **--height**.

src/imgcat.c

@@ -64,13 +64,15 @@ static struct {
     int height;
     bool use_half_height;
     bool use_fake_terminal;
+    bool should_preserve_aspect_ratio;
 } options = {
     .format = F_UNSET,          /* Default: autodetect highest fidelity. */
     .should_resize = true,      /* Default: yes! */
     .width = WIDTH_UNSET,
     .height = HEIGHT_UNSET,
     .use_half_height = false,
     .use_fake_terminal = false,
+    .should_preserve_aspect_ratio = true
 };
 
 /**
@@ -96,13 +98,14 @@ static char tempfile_name_template[NAME_MAX + 1];
 /* Long options */
 static struct option long_options[] = {
     /* Options affecting output colour depth. */
-    { "depth",          required_argument,      NULL,           'd'  },
+    { "depth",                 required_argument,      NULL,    'd'  },
 
     /* Options affecting size. */
-    { "no-resize",      no_argument,            NULL,           'R'  },
-    { "width",          required_argument,      NULL,           'w'  },
-    { "height",         required_argument,      NULL,           'r'  },
-    { "half-height",    no_argument,            NULL,           'H'  },
+    { "no-resize",                no_argument,         NULL,    'R'  },
+    { "width",                    required_argument,   NULL,    'w'  },
+    { "height",                   required_argument,   NULL,    'r'  },
+    { "half-height",              no_argument,         NULL,    'H'  },
+    { "no-preserve-aspect-ratio", no_argument,         NULL,    'P'  },
 
     /* Abbreviated options. */
     { "8",      no_argument, (int*) &options.format,    F_8_COLOR    },
@@ -198,7 +201,8 @@ int main(int argc, char **argv) {
         .max_width = terminal->width,
         .max_height = terminal->height,
         .half_height = options.use_half_height,
-        .format = color_format
+        .format = color_format,
+        .preserve_aspect_ratio = options.should_preserve_aspect_ratio
     };
     status = print_image(&request);
 
@@ -324,7 +328,7 @@ static void usage(FILE *dest) {
     const int field_width = strlen(program_name);
     fprintf(dest, "Usage:\n");
     fprintf(dest,
-            "\t%s"  " [--width=<columns> --height=<rows>|--no-resize]\n"
+            "\t%s"  " [--width=<columns> --height=<rows>|--no-resize] [--no-preserve-aspect-ratio]\n"
             "\t%*c" " [--half-height] [--depth=(8|256|24bit|iterm2)] IMAGE\n",
             program_name, field_width, ' ');
     fprintf(dest, "\t"
@@ -385,7 +389,7 @@ static const char* parse_args(int argc, char **argv) {
     opterr = 0;
 
     while (1) {
-        c = getopt_long(argc, argv, "w:r:d:RHhv", long_options, NULL);
+        c = getopt_long(argc, argv, "w:r:d:PRHhv", long_options, NULL);
         if (c == -1) {
             break;
         }
@@ -414,6 +418,10 @@ static const char* parse_args(int argc, char **argv) {
                 }
                 break;
 
+            case 'P': /* --no-preserve-aspect-ratio */
+                options.should_preserve_aspect_ratio = false;
+                break;
+
             case 'R': /* --no-resize */
                 options.should_resize = false;
                 break;

src/load_image.cc

@@ -134,6 +134,29 @@ void maybe_resize(cimg_library::CImg<unsigned char>& img, const LoadOpts& option
         /* Make sure the image is never smaller than 1x1 pixels. */
         int new_width = std::max(options.desired_width, 1);
         int new_height = std::max(options.desired_height, 1);
+
+        /* Resize preserving aspect ratio. */
+        if (options.preserve_aspect_ratio) {
+            int max_width = new_width;
+            int max_height = new_height;
+            new_width = img.width();
+            new_height = img.height();
+
+            if (new_width > max_width) {
+                new_width = max_width;
+                double ratio = ((double) img.height()) / img.width();
+                /* Scale height, ensuring it's at least 1px. */
+                new_height = std::max((int) (ratio * (double) new_width), 1);
+            }
+
+            if (new_height > max_height) {
+                new_height = max_height;
+                double ratio = ((double) img.width()) / img.height();
+                /* Scale width, ensuring it's at least 1px. */
+                new_width = std::max((int) (ratio * (double) new_height), 1);
+            }
+        }
+
         img.resize(new_width, new_height);
     } else if (resize_width) {
         /* Only resize if the image is strictly greater than the source width. */
@@ -142,7 +165,8 @@ void maybe_resize(cimg_library::CImg<unsigned char>& img, const LoadOpts& option
         }
         int new_width = options.desired_width;
         double ratio = ((double) img.height()) / img.width();
-        int new_height = ratio * (double) new_width;
+        /* Scale height, ensuring it's at least 1px. */
+        int new_height = std::max((int) (ratio * (double) new_width), 1);
         img.resize(new_width, new_height);
     } else if (resize_height) {
         /* Resize without affecting aspect ratio. */

src/load_image.h

@@ -55,6 +55,7 @@ struct LoadOpts {
     int max_height;
     int desired_width;
     int desired_height;
+    bool preserve_aspect_ratio;
 };
 
 /**

src/print_image.c

@@ -88,6 +88,7 @@ static bool print_iterate(PrintRequest *request) {
         .max_height = request->max_height,
         .desired_width = request->desired_width,
         .desired_height = request->desired_height,
+        .preserve_aspect_ratio = request->preserve_aspect_ratio,
     };
     assert(format != F_UNSET);
 

src/print_image.h

@@ -44,6 +44,7 @@ typedef struct {
     int desired_width;
     int desired_height;
     bool half_height;
+    bool preserve_aspect_ratio;
     Format format;
 } PrintRequest;