这个程序应该从缓冲区中读取有关位图的信息。 它是用Python3.8编写的。
问题就出在这行代码上。
image_w, image_h, image_bpp, image_data = MyLoadBMP("test.bmp")
编译器会吐出错误:
TypeError: cannot unpack non-iterable NoneType object
我想错误可能是在变量的定义上，但是我不知道如何改变它。 变量是这样定义的。
这是提示，它没有改变代码。
image_w:union[无，未知]image_h:union[无，未知]image_bpp:union[无，未知]image_data:union[无，未知]
下面，我将附加与bug相关的定义函数。
def MyLoadBMP(filename):
# Read the entire file into the buffer.
with open(filename, "rb") as f:
data = f.read()
if data[:2] != 'BM':
# Invalid BMP file.
return None
# Will extract BITMAPFILEHEADER
bfType, bfSize, bfRes1, bfRes2, bfOffBits = struct.unpack("<HIHHI", data[:14])
# Will extract BITMAPINFOHEADER.
(biSize, biWidth, biHeight, biPlanes, biBitCount, biCompression, biSizeImage, biXPelsPerMeter, biYPelsPerMeter, biClrUser, biClrImportant) = struct.unpack("<IIIHHIIIIII", data[14:14 + 40])
if biSize != 40:
# Unsupported BMP variant.
return None
if biBitCount == 24 and biCompression == 0: #BI_RGB
return MyLoadBMP_RGB24(data, bfOffBits, biWidth, biHeight)
# Encoding not supported.
return None
def MyLoadBMP_RGB24(data, pixel_offset, w, h):
# Are the poems written from bottom to top?
bottom_up = True
if h < 0:
bottom_up = False
h = - h
# Calculate the pitch.
pitch = (w * 3 + 3) & ~3
# Create a new buffer for the read bitmap (24BPP, color order: BGR).
bitmap = array.array('B', [0]) * w * h * 3
# Load lines.
if bottom_up:
r = range(h - 1, -1, -1)
else:
r = range(0, h)
for y in r:
for x in range(0, w):
bitmap[(x + y * w * 3 + 0)] = ord(data[pixel_offset + x * 3 + 0])
bitmap[(x + y * w * 3 + 1)] = ord(data[pixel_offset + x * 3 + 1])
bitmap[(x + y * w * 3 + 2)] = ord(data[pixel_offset + x * 3 + 2])
pixel_offset += pitch
return (w, h, 24, bitmap)
您的函数返回none，可能是因为您在代码中遇到了以下三种情况之一:
if data[:2] != 'BM':
# Invalid BMP file.
return None
# ...
if biSize != 40:
# Unsupported BMP variant.
return None
if biBitCount == 24 and biCompression == 0: #BI_RGB
# ...
# Encoding not supported.
return None
无法解压缩无:
>>> image_w, image_h, image_bpp, image_data = None
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'NoneType' object is not iterable
先测试结果，然后解包:
result = MyLoadBMP("test.bmp")
if result is None:
# handle separately
else:
image_w, image_h, image_bpp, image_data = result
