lv_img_conv_py: minimal python port of node module

Create a minimal python port of the node.js module `lv_img_conv`. Only
the currently in use color formats `CF_INDEXED_1_BIT` and
`CF_TRUE_COLOR_ALPHA` are implemented.

Output only as binary with format `ARGB8565_RBSWAP`.

This is enough to create the `resources-1.13.0.zip`.

Python3 implements "propper" "banker's rounding" by rounding to the nearest
even number. Javascript rounds to the nearest integer.
To have the same output as the original JavaScript implementation add a custom
rounding function, which does "school" rounding (to the nearest integer)

Update CMake file in `resources` folder to call `lv_img_conf.py` instead of
node module.

For docker-files install `python3-pil` package for `lv_img_conv.py` script.
And remove the `lv_img_conv` node installation.

---

gen_img: special handling for python lv_img_conv script

Not needed on Linux systems, as the shebang of the python script is read
and used. But just to be sure use the python interpreter found by CMake.
Also helps if tried to run on Windows host.

---

doc: buildAndProgram: remove node script lv_img_conv mention

Remove node script `lv_img_conv` mention and replace it for
runtime-depency `python3-pil` of python script `lv_img_conv.py`.

.devcontainer/Dockerfile

@@ -11,6 +11,7 @@ RUN apt-get update -qq \
       make \
       python3 \
       python3-pip \
+      python3-pil \
       tar \
       unzip \
       wget \ 

doc/buildAndProgram.md

@@ -42,7 +42,7 @@ CMake configures the project according to variables you specify the command line
 **NRF5_SDK_PATH**|path to the NRF52 SDK|`-DNRF5_SDK_PATH=/home/jf/nrf52/Pinetime/sdk`|
 **CMAKE_BUILD_TYPE (\*)**| Build type (Release or Debug). Release is applied by default if this variable is not specified.|`-DCMAKE_BUILD_TYPE=Debug`
 **BUILD_DFU (\*\*)**|Build DFU files while building (needs [adafruit-nrfutil](https://github.com/adafruit/Adafruit_nRF52_nrfutil)).|`-DBUILD_DFU=1`
-**BUILD_RESOURCES (\*\*)**| Generate external resource while building (needs [lv_font_conv](https://github.com/lvgl/lv_font_conv) and [lv_img_conv](https://github.com/lvgl/lv_img_conv). |`-DBUILD_RESOURCES=1`
+**BUILD_RESOURCES (\*\*)**| Generate external resource while building (needs [lv_font_conv](https://github.com/lvgl/lv_font_conv) and [python3-pil/pillow](https://pillow.readthedocs.io) module). |`-DBUILD_RESOURCES=1`
 **TARGET_DEVICE**|Target device, used for hardware configuration. Allowed: `PINETIME, MOY-TFK5, MOY-TIN5, MOY-TON5, MOY-UNK`|`-DTARGET_DEVICE=PINETIME` (Default)
 
 #### (\*) Note about **CMAKE_BUILD_TYPE**

docker/Dockerfile

@@ -11,6 +11,7 @@ RUN apt-get update -qq \
       make \
       python3 \
       python3-pip \
+      python3-pil \
       python-is-python3 \
       tar \
       unzip \
@@ -39,10 +40,6 @@ RUN pip3 install -Iv cryptography==3.3
 RUN pip3 install cbor
 RUN npm i [email protected] -g
 
-RUN npm i [email protected] -g
-RUN npm i @swc/core -g
-RUN npm i [email protected] -g
-
 # build.sh knows how to compile
 COPY build.sh /opt/
 

src/resources/CMakeLists.txt

@@ -3,8 +3,8 @@ find_program(LV_FONT_CONV "lv_font_conv" NO_CACHE REQUIRED
     HINTS "${CMAKE_SOURCE_DIR}/node_modules/.bin")
 message(STATUS "Using ${LV_FONT_CONV} to generate font files")
 
-find_program(LV_IMG_CONV "lv_img_conv" NO_CACHE REQUIRED
-    HINTS "${CMAKE_SOURCE_DIR}/node_modules/.bin")
+find_program(LV_IMG_CONV "lv_img_conv.py" NO_CACHE REQUIRED
+    HINTS "${CMAKE_CURRENT_SOURCE_DIR}")
 message(STATUS "Using ${LV_IMG_CONV} to generate font files")
 
 if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.12)

src/resources/generate-img.py

@@ -11,6 +11,9 @@
 
 def gen_lvconv_line(lv_img_conv: str, dest: str, color_format: str, output_format: str, binary_format: str, sources: str):
     args = [lv_img_conv, sources, '--force', '--output-file', dest, '--color-format', color_format, '--output-format', output_format, '--binary-format', binary_format]
+    if lv_img_conv.endswith(".py"):
+        # lv_img_conv is a python script, call with current python executable
+        args = [sys.executable] + args
 
     return args
 

src/resources/lv_img_conv.py

@@ -0,0 +1,193 @@
+#!/usr/bin/env python3
+import argparse
+import pathlib
+import sys
+import decimal
+from PIL import Image
+
+
+def classify_pixel(value, bits):
+    def round_half_up(v):
+        """python3 implements "propper" "banker's rounding" by rounding to the nearest
+        even number. Javascript rounds to the nearest integer.
+        To have the same output as the original JavaScript implementation add a custom
+        rounding function, which does "school" rounding (to the nearest integer).
+
+        see: https://stackoverflow.com/questions/43851273/how-to-round-float-0-5-up-to-1-0-while-still-rounding-0-45-to-0-0-as-the-usual
+        """
+        return int(decimal.Decimal(v).quantize(decimal.Decimal('1'), rounding=decimal.ROUND_HALF_UP))
+    tmp = 1 << (8 - bits)
+    val = round_half_up(value / tmp) * tmp
+    if val < 0:
+        val = 0
+    return val
+
+
+def test_classify_pixel():
+    # test difference between round() and round_half_up()
+    assert classify_pixel(18, 5) == 16
+    # school rounding 4.5 to 5, but banker's rounding 4.5 to 4
+    assert classify_pixel(18, 6) == 20
+
+
+def main():
+    parser = argparse.ArgumentParser()
+
+    parser.add_argument("img",
+        help="Path to image to convert to C header file")
+    parser.add_argument("-o", "--output-file",
+        help="output file path (for single-image conversion)",
+        required=True)
+    parser.add_argument("-f", "--force",
+        help="allow overwriting the output file",
+        action="store_true")
+    parser.add_argument("-i", "--image-name",
+        help="name of image structure (not implemented)")
+    parser.add_argument("-c", "--color-format",
+        help="color format of image",
+        default="CF_TRUE_COLOR_ALPHA",
+        choices=[
+            "CF_ALPHA_1_BIT", "CF_ALPHA_2_BIT", "CF_ALPHA_4_BIT",
+            "CF_ALPHA_8_BIT", "CF_INDEXED_1_BIT", "CF_INDEXED_2_BIT", "CF_INDEXED_4_BIT",
+            "CF_INDEXED_8_BIT", "CF_RAW", "CF_RAW_CHROMA", "CF_RAW_ALPHA",
+            "CF_TRUE_COLOR", "CF_TRUE_COLOR_ALPHA", "CF_TRUE_COLOR_CHROMA", "CF_RGB565A8",
+        ],
+        required=True)
+    parser.add_argument("-t", "--output-format",
+        help="output format of image",
+        default="bin", # default in original is 'c'
+        choices=["c", "bin"])
+    parser.add_argument("--binary-format",
+        help="binary color format (needed if output-format is binary)",
+        default="ARGB8565_RBSWAP",
+        choices=["ARGB8332", "ARGB8565", "ARGB8565_RBSWAP", "ARGB8888"])
+    parser.add_argument("-s", "--swap-endian",
+        help="swap endian of image (not implemented)",
+        action="store_true")
+    parser.add_argument("-d", "--dither",
+        help="enable dither (not implemented)",
+        action="store_true")
+    args = parser.parse_args()
+
+    img_path = pathlib.Path(args.img)
+    out = pathlib.Path(args.output_file)
+    if not img_path.is_file():
+        print(f"Input file is missing: '{args.img}'")
+        return 1
+    print(f"Beginning conversion of {args.img}")
+    if out.exists():
+        if args.force:
+            print(f"overwriting {args.output_file}")
+        else:
+            pritn(f"Error: refusing to overwrite {args.output_file} without -f specified.")
+            return 1
+    out.touch()
+
+    # only implemented the bare minimum, everything else is not implemented
+    if args.color_format not in ["CF_INDEXED_1_BIT", "CF_TRUE_COLOR_ALPHA"]:
+        raise NotImplementedError(f"argument --color-format '{args.color_format}' not implemented")
+    if args.output_format != "bin":
+        raise NotImplementedError(f"argument --output-format '{args.output_format}' not implemented")
+    if args.binary_format not in ["ARGB8565_RBSWAP", "ARGB8888"]:
+        raise NotImplementedError(f"argument --binary-format '{args.binary_format}' not implemented")
+    if args.image_name:
+        raise NotImplementedError(f"argument --image-name not implemented")
+    if args.swap_endian:
+        raise NotImplementedError(f"argument --swap-endian not implemented")
+    if args.dither:
+        raise NotImplementedError(f"argument --dither not implemented")
+
+    # open image using Pillow
+    img = Image.open(img_path)
+    img_height = img.height
+    img_width = img.width
+    if args.color_format == "CF_TRUE_COLOR_ALPHA" and args.binary_format == "ARGB8888":
+        buf = bytearray(img_height*img_width*4) # 4 bytes (32 bit) per pixel
+        for y in range(img_height):
+            for x in range(img_width):
+                i = (y*img_width + x)*4 # buffer-index
+                pixel = img.getpixel((x,y))
+                r, g, b, a = pixel
+                buf[i + 0] = r
+                buf[i + 1] = g
+                buf[i + 2] = b
+                buf[i + 3] = a
+
+    elif args.color_format == "CF_TRUE_COLOR_ALPHA" and args.binary_format == "ARGB8565_RBSWAP":
+        buf = bytearray(img_height*img_width*3) # 3 bytes (24 bit) per pixel
+        for y in range(img_height):
+            for x in range(img_width):
+                i = (y*img_width + x)*3 # buffer-index
+                pixel = img.getpixel((x,y))
+                r_act = classify_pixel(pixel[0], 5)
+                g_act = classify_pixel(pixel[1], 6)
+                b_act = classify_pixel(pixel[2], 5)
+                a = pixel[3]
+                r_act = min(r_act, 0xF8)
+                g_act = min(g_act, 0xFC)
+                b_act = min(b_act, 0xF8)
+                c16 = ((r_act) << 8) | ((g_act) << 3) | ((b_act) >> 3) # RGR565
+                buf[i + 0] = (c16 >> 8) & 0xFF
+                buf[i + 1] = c16 & 0xFF
+                buf[i + 2] = a
+
+    elif args.color_format == "CF_INDEXED_1_BIT": # ignore binary format, use color format as binary format
+        w = img_width >> 3
+        if img_width & 0x07:
+            w+=1
+        max_p = w * (img_height-1) + ((img_width-1) >> 3) + 8  # +8 for the palette
+        buf = bytearray(max_p+1)
+
+        for y in range(img_height):
+            for x in range(img_width):
+                c, a = img.getpixel((x,y))
+                p = w * y + (x >> 3) + 8  # +8 for the palette
+                buf[p] |= (c & 0x1) << (7 - (x & 0x7))
+        # write palette information, for indexed-1-bit we need palette with two values
+        # write 8 palette bytes
+        buf[0] = 0
+        buf[1] = 0
+        buf[2] = 0
+        buf[3] = 0
+        # Normally there is much math behind this, but for the current use case this is close enough
+        # only needs to be more complicated if we have more than 2 colors in the palette
+        buf[4] = 255
+        buf[5] = 255
+        buf[6] = 255
+        buf[7] = 255
+    else:
+        # raise just to be sure
+        raise NotImplementedError(f"args.color_format '{args.color_format}' with args.binary_format '{args.binary_format}' not implemented")
+
+    # write header
+    match args.color_format:
+        case "CF_TRUE_COLOR_ALPHA":
+            lv_cf = 5
+        case "CF_INDEXED_1_BIT":
+            lv_cf = 7
+        case _:
+            # raise just to be sure
+            raise NotImplementedError(f"args.color_format '{args.color_format}' not implemented")
+    header_32bit = lv_cf | (img_width << 10) | (img_height << 21)
+    buf_out = bytearray(4 + len(buf))
+    buf_out[0] = header_32bit & 0xFF
+    buf_out[1] = (header_32bit & 0xFF00) >> 8
+    buf_out[2] = (header_32bit & 0xFF0000) >> 16
+    buf_out[3] = (header_32bit & 0xFF000000) >> 24
+    buf_out[4:] = buf
+
+    # write byte buffer to file
+    with open(out, "wb") as f:
+        f.write(buf_out)
+    return 0
+
+
+if __name__ == '__main__':
+    if "--test" in sys.argv:
+        # run small set of tests and exit
+        print("running tests")
+        test_classify_pixel()
+        print("success!")
+        sys.exit(0)
+    # run normal program
+    sys.exit(main())