Question

生成图像直方图，将jpeg文件读入24位数组并将其转换为32位numpy文件，以便使用numpy.histogram进行处理，遵循以下方法：

将文件读成numpy数组形状：（w，h，3） - ＆gt; img=imread(file,'RGB')
转换为字节块大小：w * h * 3 - ＆gt; by=img.tobytes()
使用struct iterator解压缩 - ＆gt; struct.iter_unpack('<3B',by)
转换为int - ＆gt; int.from_bytes(c, byteorder='big')

这种方法的问题和我尝试的其他问题（重塑为w * h，3等）是迭代器延迟，我的问题是：

在没有迭代器的python 中有直接方法，或者我应该编写一个简单的C函数来执行此操作吗？

def jpeg2colors(fnme): return np.asarray( [int.from_bytes(c, byteorder='big') for c in struct.iter_unpack('<3B', imread(fnme).tobytes())])

其他较慢的实现：

def conversionSLOW(fnme): # reshape to (w*h,3) img = imread(fnme, mode='RGB') return np.array([int.from_bytes(c, byteorder='big') for c in img.reshape((img.shape[0] * img.shape[1], 3))]) def conversionbyte01(fnme): # int iteration -> closer to fastests by = imread(fnme, mode='RGB').tobytes() return np.asanyarray([int.from_bytes(by[c:c + 3], byteorder='big') for c in range(0, len(by) - 3, 3)], dtype=np.int32) def conversionbyte02(fnme): img = imread(fnme) return np.array([int.from_bytes(c, byteorder='big') for c in img.reshape(img.shape[0] * img.shape[1], 3)]) def conversionbyte03(fnme): img = imread(fnme) return np.array([int.from_bytes(img.reshape(img.shape[0] * img.shape[1], 3), byteorder='big')])

EDIT1：

找到一个解决方案，创建一个（w，h，4）numpy数组并复制读取图像，休息简单快速（ x40 从最快的迭代解决方案改进）

def fromJPG2_2int32_stbyst(fnme): # step by step img = imread(fnme) # create a (w,h,4) array and copy original re = np.zeros((img.shape[0], img.shape[1], 4), dtype=np.uint8) re[:, :, :-1] = img # lineup to a byte structure ready for ' frombuffer' re1 = re.reshape(img.shape[0] * img.shape[1] * 4) by = re1.tobytes() # got it just convert to int cols = np.frombuffer(by, 'I') return cols def fromJPG2_2int32_v0(fnme): # more compact & efficient img = imread(fnme) re = np.zeros((img.shape[0], img.shape[1], 4), dtype=np.uint8) re[:, :, :-1] = img return np.frombuffer(re.reshape(img.shape[0] * img.shape[1] * 4).tobytes(), 'I') def fromJPG2_2int32(fnme): # even better using numpy.c_[] img = imread(fnme) img = np.c_[img, np.zeros((img.shape[0], img.shape[1], 1), dtype=np.uint8)] return np.frombuffer(img.reshape(img.shape[0] * img.shape[1] * 4).tobytes(), 'I')

Answer 1

溶液：

    def fromjpg2int32(fnme):  # convert jpg 2 int color array
    img = imread(fnme)
    return np.frombuffer(
        np.insert(img, 3, values=0, axis=2).
            reshape(img.shape[0] * img.shape[1] * 4).tobytes(), 'I')

python jpeg文件24到32位转换

1 个答案: