Merge pull request #7 from tannewt/use_bitmap_subscr

Simplify load and use [] on the bitmap

Author: tannewt

README.rst

@@ -20,7 +20,7 @@ overhead of the decoding code.
 Usage Example
 =============
 
-.. literalinclude:: examples/imageload_simpletest.py
+.. literalinclude:: ../examples/imageload_simpletest.py
 
 Contributing
 ============

adafruit_imageload/__init__.py

@@ -41,11 +41,10 @@ def load(filename, *, bitmap=None, palette=None):
        palette is the desired pallete type. The constructor should take the number of colors and
        support assignment to indices via [].
     """
-    with open(filename, "rb") as f:
-        header = f.read(3)
+    with open(filename, "rb") as file:
+        header = file.read(3)
         if header.startswith(b"BM"):
             from . import bmp
-            f.seek(0)
-            return bmp.load(f, bitmap=bitmap, palette=palette)
-        else:
-            raise RuntimeError("Unsupported image format")
+            file.seek(0)
+            return bmp.load(file, bitmap=bitmap, palette=palette)
+        raise RuntimeError("Unsupported image format")

adafruit_imageload/bmp/__init__.py

@@ -32,25 +32,33 @@
 __version__ = "0.0.0-auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_ImageLoad.git"
 
-def load(f, *, bitmap=None, palette=None):
-    f.seek(10)
-    data_start = int.from_bytes(f.read(4), 'little')
+def load(file, *, bitmap=None, palette=None):
+    """Loads a bmp image from the open ``file``.
+
+       Returns tuple of bitmap object and palette object.
+
+       :param object bitmap: Type to store bitmap data. Must have API similar to `displayio.Bitmap`.
+         Will be skipped if None
+       :param object palette: Type to store the palette. Must have API similar to
+         `displayio.Palette`. Will be skipped if None"""
+    file.seek(10)
+    data_start = int.from_bytes(file.read(4), 'little')
     # f.seek(14)
-    # bmp_header_length = int.from_bytes(f.read(4), 'little')
+    # bmp_header_length = int.from_bytes(file.read(4), 'little')
     # print(bmp_header_length)
-    f.seek(18)
-    width = int.from_bytes(f.read(4), 'little')
-    height = int.from_bytes(f.read(4), 'little')
-    f.seek(28)
-    color_depth = int.from_bytes(f.read(2), 'little')
-    f.seek(46)
-    colors = int.from_bytes(f.read(4), 'little')
-
-    compute_palette = False
+    file.seek(0x12) # Width of the bitmap in pixels
+    width = int.from_bytes(file.read(4), 'little')
+    height = int.from_bytes(file.read(4), 'little')
+    file.seek(0x1c) # Number of bits per pixel
+    color_depth = int.from_bytes(file.read(2), 'little')
+    file.seek(0x2e) # Number of colors in the color palette
+    colors = int.from_bytes(file.read(4), 'little')
+
     if colors == 0 and color_depth >= 16:
         raise NotImplementedError("True color BMP unsupported")
     else:
         if colors == 0:
             colors = 2 ** color_depth
         from . import indexed
-        return indexed.load(f, width, height, data_start, colors, color_depth, bitmap=bitmap, palette=palette)
+        return indexed.load(file, width, height, data_start, colors, color_depth, bitmap=bitmap,
+                            palette=palette)

adafruit_imageload/bmp/indexed.py

@@ -32,52 +32,50 @@
 __version__ = "0.0.0-auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_ImageLoad.git"
 
-import math
-
-def load(f, width, height, data_start, colors, color_depth, *, bitmap=None, palette=None):
+def load(file, width, height, data_start, colors, color_depth, *, bitmap=None, palette=None):
+    """Loads indexed bitmap data into bitmap and palette objects.
+
+       :param file file: The open bmp file
+       :param int width: Image width in pixels
+       :param int height: Image height in pixels
+       :param int data_start: Byte location where the data starts (after headers)
+       :param int colors: Number of distinct colors in the image
+       :param int color_depth: Number of bits used to store a value"""
+    # pylint: disable=too-many-arguments,too-many-locals
     if palette:
         palette = palette(colors)
 
-        f.seek(data_start - colors * 4)
-        for color in range(colors):
-            c = f.read(4)
-            palette[color] = c
+        file.seek(data_start - colors * 4)
+        for value in range(colors):
+            c_bytes = file.read(4)
+            # Need to swap red & blue bytes (bytes 0 and 2)
+            palette[value] = bytes(b''.join([c_bytes[2:3],
+                                             c_bytes[1:2],
+                                             c_bytes[0:1],
+                                             c_bytes[3:1]]))
 
     if bitmap:
         minimum_color_depth = 1
         while colors > 2 ** minimum_color_depth:
             minimum_color_depth *= 2
 
         bitmap = bitmap(width, height, colors)
-        f.seek(data_start)
+        file.seek(data_start)
         line_size = width // (8 // color_depth)
         if line_size % 4 != 0:
             line_size += (4 - line_size % 4)
 
-        packed_pixels = None
-        if color_depth != minimum_color_depth and minimum_color_depth == 2:
-            target_line_size = width // 4
-            if target_line_size % 4 != 0:
-                target_line_size += (4 - target_line_size % 4)
-
-            packed_pixels = bytearray(target_line_size)
-
-        for line in range(height-1,-1,-1):
-            chunk = f.read(line_size)
-            if packed_pixels:
-                original_pixels_per_byte = 8 // color_depth
-                packed_pixels_per_byte = 8 // minimum_color_depth
-
-                for i in range(width // packed_pixels_per_byte):
-                    packed_pixels[i] = 0
+        chunk = bytearray(line_size)
+        mask = (1 << minimum_color_depth) - 1
 
-                for i in range(width):
-                    pi = i // packed_pixels_per_byte
-                    ci = i // original_pixels_per_byte
-                    packed_pixels[pi] |= ((chunk[ci] >> (8 - color_depth*(i % original_pixels_per_byte + 1))) & 0x3) << (8 - minimum_color_depth*(i % packed_pixels_per_byte + 1))
+        for y in range(height - 1, -1, -1):
+            file.readinto(chunk)
+            pixels_per_byte = 8 // color_depth
+            offset = y * width
 
-                bitmap._load_row(line, packed_pixels)
-            else:
-                bitmap._load_row(line, chunk)
+            for x in range(width):
+                i = x // pixels_per_byte
+                pixel = (chunk[i] >> (8 - color_depth*(x % pixels_per_byte + 1))) & mask
+                bitmap[offset + x] = pixel
 
     return bitmap, palette

docs/developing.rst

@@ -102,16 +102,16 @@ The corresponding Bitmap to the example above appears like this after loading::
     4   4   4   5   5   5  12  12  12   5   5   5   7   7   7
     5   5   5   5   5   5   5   5   5   5   5   5   5   5   5
 
-This grid represents the example image (`15 pixels wide` and  `17 pixels tall`).
-The coordinates are arranged in a zero indexed grid, starting in the top left at `[0,0]`,
-and continuing down and to the right to a final coordinate of `[14,16]`.
+This grid represents the example image (``15 pixels wide`` and  ``17 pixels tall``).
+The coordinates are arranged in a zero indexed grid, starting in the top left at ``[0,0]``,
+and continuing down and to the right to a final coordinate of ``[14,16]``.
 
 
 The value at each position is an integer, representing an entry in the palette object.
 
 
 
-For example, the Bitmap coordinate `[0,0]` has the value (integer) `5`.
+For example, the Bitmap coordinate ``[0,0]`` has the value (integer) ``5``.
 
 
-This corresponds to the the Palette object's, `[5]` which is `b'\x00\x00\xff\x00'`. This is a byte string that represents a color.
+This corresponds to the the Palette object's, ``[5]`` which is ``b'\x00\x00\xff\x00'``. This is a byte string that represents a color.

docs/index.rst

@@ -23,15 +23,15 @@ Table of Contents
 .. toctree::
     :caption: Tutorials
 
-.. todo:: Add any Learn guide links here. If there are none, then simply delete this todo and leave
-    the toctree above for use later.
+.. toctree::
+    :caption: Development
+    :maxdepth: 3
+
+    developing
 
 .. toctree::
     :caption: Related Products
 
-.. todo:: Add any product links here. If there are none, then simply delete this todo and leave
-    the toctree above for use later.
-
 .. toctree::
     :caption: Other Links
 

examples/imageload_colorwheel.py

@@ -0,0 +1,17 @@
+import board
+import displayio
+import adafruit_imageload
+
+display = board.DISPLAY
+
+bitmap, palette = adafruit_imageload.load("images/color_wheel.bmp",
+                                          bitmap=displayio.Bitmap,
+                                          palette=displayio.Palette)
+
+tile_grid = displayio.TileGrid(bitmap, pixel_shader=palette)
+
+group = displayio.Group()
+group.append(tile_grid)
+display.show(group)
+while True:
+    pass

examples/imageload_simpletest.py

@@ -1,4 +1,6 @@
 import displayio
 import adafruit_imageload
 
-image, palette = adafruit_imageload.load("images/4bit.bmp", bitmap=displayio.Bitmap, palette=displayio.Palette)
+image, palette = adafruit_imageload.load("images/4bit.bmp",
+                                         bitmap=displayio.Bitmap,
+                                         palette=displayio.Palette)