Add --font-scale, --h-padding, --v-shift and generalize --end-margin

Fixes #2

Author: Ircama

README.md

@@ -34,10 +34,10 @@ In addition, all options included in *labelmaker.py* are available, with several
 ```
 usage: printlabel.py [-h] [-u] [-l] [-s] [-c] [-i FILE_NAME] [-M FILE_NAME] [-R FLOAT] [-X DOTS]
                      [-Y DOTS] [-S FILE_NAME] [-n] [-F] [-a] [-m DOTS] [-r] [-C]
-                     [--fill-color FILL] [--stroke-fill STROKE_FILL]
-                     [--stroke-width STROKE_WIDTH] [--text-size MILLIMETERS]
-                     [--white-level NUMBER] [--threshold NUMBER]
-                     COM_PORT FONT_NAME TEXT_TO_PRINT [TEXT_TO_PRINT ...]
+                     [--fill-color FILL] [--stroke-fill STROKE_FILL] [--stroke-width STROKE_WIDTH]
+                     [--text-size MILLIMETERS] [--font-scale NUMBER] [--h-padding DOTS]
+                     [--v-shift DOTS] [--white-level NUMBER] [--threshold NUMBER]
+                     COM_PORT [FONT_NAME] [TEXT_TO_PRINT ...]
 
 positional arguments:
   COM_PORT              Printer COM port.
@@ -78,15 +78,20 @@ optional arguments:
                         Width of the text stroke (e.g., 1 or 2).
   --text-size MILLIMETERS
                         Horizontally stretch the text to fit the specified size.
-  --white-level NUMBER  Minimum pixel value to consider it "white" when cropping the image. Set
-                        it to a value close to 255. (Default: 240)
+  --font-scale NUMBER   Scale font size by specified percentage (default: 100%)
+  --h-padding DOTS      Define custom left and right horizontal padding in pixels (default: 5
+                        pixels left and 5 pixels right)
+  --v-shift DOTS        Define relative vertical traslation in pixels (default is to vertically
+                        center the font)
+  --white-level NUMBER  Minimum pixel value to consider it "white" when cropping the image. Set it
+                        to a value close to 255. (Default: 240)
   --threshold NUMBER    Custom thresholding when converting the image to binary, to manually
                         decide which pixel values become black or white (Default: 75)
 ```
 
 Options `-sln` are useful to simulate the print, showing the created image and adding a ruler in inches and centimeters (magenta), with horizontal lines to mark the drawing area (dotted red) and the tape borders (cyan).
 
-Before generating the text (`TEXT_TO_PRINT`), the tool allows concatenating images with the `-M` option; it can be used more times for multiple images (transparent images are also accepted). The final image can also be saved with the `-S` option and then reused by running again the tool with the `-M` option; when also setting `TEXT_TO_PRINT` to a null string (`""`), the reused image will remain unchanged. Merged images are automatically resized to fit the printable area, removing white borders without modifying the proportion. Resize and traslation of merged images can also be manually controlled with `-R` (floating point number), `-X`, `-Y`. The `--text-size` option horizontally stretches or squeezes the text so that it fits the specified size in millimeters; the size parameter includes `--end-margin` and default left and right paddings, but does not include the size of merged images if used, which have a fixed length that has to be kept proportioned.
+Before generating the text (`TEXT_TO_PRINT`), the tool allows concatenating images with the `-M` option; it can be used more times for multiple images (transparent images are also accepted). The final image can also be saved with the `-S` option and then reused by running again the tool with the `-M` option; when also setting `TEXT_TO_PRINT` to a null string (`""`), the reused image will remain unchanged. Merged images are automatically resized to fit the printable area, removing white borders without modifying the proportion. Resize and traslation of merged images can also be manually controlled with `-R` (floating point number), `-X`, `-Y`. The `--text-size` option horizontally stretches or squeezes the text so that it fits the specified size in millimeters; the size parameter includes `--end-margin` and default left and right paddings, but does not include the size of merged images if used, which have a fixed length that has to be kept proportioned. The `font-scale` allows specifying a percentage to scale the font size, maintaining the aspect ratio; font sizes > 100 are accepted even if potentially causing overflow. `--h-padding` and `--v-shift` allow horizontally and vertically traslating the text (using `--h-padding` with `--end-margin` enables separately cointrolling left and right margins; specifically `--h-padding` uses the same value for the left and right parts, while `--end-margin` will be a relative value applied to the right `--h-padding`).
 
 `-i` runs the legacy process of *labelmaker.py* and disables image processing.
 

printlabel.py

@@ -145,6 +145,29 @@ def set_args():
         type=int,
         default=None,
     )
+    p.add_argument(
+        '--font-scale',
+        type=float,
+        default=None,
+        metavar='NUMBER',
+        help='Scale font size by specified percentage (default: 100%%)'
+    )
+    p.add_argument(
+        '--h-padding',
+        type=int,
+        default=5,
+        metavar='DOTS',
+        help='Define custom left and right horizontal padding in pixels'
+        ' (default: 5 pixels left and 5 pixels right)'
+    )
+    p.add_argument(
+        '--v-shift',
+        type=int,
+        default=0,
+        metavar='DOTS',
+        help='Define relative vertical traslation in pixels'
+        ' (default is to vertically center the font)'
+    )
     p.add_argument(
         '--white-level',
         help='Minimum pixel value to consider it "white" when'
@@ -242,7 +265,6 @@ def main():
         height_of_the_printable_area = 64  # px: number of vertical pixels of the PT-P300BT printer (9 mm)
         height_of_the_tape = 86  # 64 px / 9 mm * 12 mm (the borders over the printable area will not be printed)
         height_of_the_image = 88  # px (can be any value >= height_of_the_tape, but height_of_the_tape + 2 border lines is good)
-        h_padding = 5  # horizontal padding (left and right)
 
         # Compute max TT font size to remain within height_of_the_printable_area
         font_size = 0
@@ -273,16 +295,37 @@ def main():
                         f' instead of {height_of_the_printable_area}.')
                     break
 
+            y_position = print_border
+            if args.font_scale:
+                scaled_font_size = int(
+                    round(font_size * (args.font_scale / 100.0))
+                )
+                try:
+                    font = ImageFont.truetype(
+                        args.fontname, scaled_font_size, encoding='utf-8'
+                    )
+                except Exception as e:
+                    p.error(f'Cannot load font "{args.fontname}" - {e}')
+                font_width, font_height = font.getbbox(text, anchor="lt")[2:]
+
+                # Vertically center text
+                y_position = print_border + (
+                    height_of_the_printable_area - font_height
+                ) // 2
+
             # Create a drawing context for the image
             image = Image.new(
                 "RGB",
-                (font_width + h_padding * 2 + 1, height_of_the_image),
+                (
+                    font_width + args.h_padding * 2 + 1 + args.end_margin,
+                    height_of_the_image
+                ),
                 "white"
             )
             draw = ImageDraw.Draw(image)
             try:
                 draw.text(
-                    (h_padding, print_border), text,
+                    (args.h_padding, y_position + args.v_shift), text,
                     font=font,
                     fill=args.fill,
                     anchor="lt",
@@ -294,7 +337,7 @@ def main():
             if args.text_size:
                 text_size = (
                     int(args.text_size / 0.149)
-                    - h_padding
+                    - args.h_padding
                     - args.end_margin
                 )  # mm to dot
                 _, _, text_width, text_height = draw.textbbox(
@@ -305,7 +348,7 @@ def main():
                 )
                 scale_factor = text_width / text_size
                 image = image.transform(
-                    (text_size + args.end_margin, height_of_the_image),
+                    (text_size + args.end_margin + args.h_padding, height_of_the_image),
                     Image.Transform.AFFINE,
                     (scale_factor, 0, 0, 0, 1, 0),
                 )