将 pgm 转换为 png

我的文件夹中有 100 个 pgm 图像，我想将这些图像转换为 png 格式。我使用了这段代码，但是当我打开它时，结果图像要么是黑色的，要么只是正确构建的图像的一部分，而其他部分是黑色的： 我使用了这段代码，但是还有其他想法来转换这些图像吗？

import os
from PIL import Image

def convert_pgm_to_png(pgm_path, png_path):
    # Open the PGM image in binary mode
    with open(pgm_path, 'rb') as f:
        # Read the header to extract image dimensions
        header = f.readline().decode('latin-1').strip()
        
        if header.startswith('P5'):
            # Split the header line to extract width, height, and maximum gray value
            dimensions = header.split()[1:]
            width, height = map(int, dimensions[:2])
            
            # Validate the maximum gray value
            max_gray_value = int(dimensions[2])
            if max_gray_value > 255:
                raise ValueError('Invalid PGM file format. Maximum gray value exceeds 255.')
            
            # Read the binary data
            data = f.read()
        
        else:
            raise ValueError('Invalid PGM file format. Magic number is not "P5".')
    
    # Convert binary data to a list of pixel values
    pixels = list(data)
    
    print(f"Pixel values: {pixels}")  # Print the pixel values
    
    # Create a new PIL Image object with appropriate mode and size
    image = Image.new('L', (width, height))
    
    # Assign the pixel values to the image
    image.putdata(pixels)
    
    # Save the image as PNG in the destination directory
    image.save(png_path)

# Source directory containing PGM images
source_directory = "C:\\Users\\Sara\\Desktop\\dataasets\\Newfolder\\lr(compressed)_pgm"

# Destination directory to save PNG images
destination_directory = "C:\\Users\\Sara\\Desktop\\dataasets\\Newfolder\\lr\\"

# Iterate over all files in the source directory
for filename in os.listdir(source_directory):
    if filename.endswith('.pgm'):
        # Create the input file path for PGM image
        pgm_file = os.path.join(source_directory, filename)
        
        # Create the output file path for PNG image in the destination directory
        png_file = os.path.join(destination_directory, os.path.splitext(filename)[0] + '.png')
        
        try:
            # Convert PGM to PNG
            convert_pgm_to_png(pgm_file, png_file)
        except ValueError as e:
            header = ""
            with open(pgm_file, 'rb') as f:
                header = f.readline().decode('latin-1').strip()
            print(f"Error converting {pgm_file}: {str(e)}") 

问题出在读取二进制图像数据的方式上。虽然 f.read() 读取了所有剩余的字节，但在某些情况下，PGM 文件中可能存在注释或空格，这些注释或空格会干扰像素数据的读取。

请尝试使用此改进的代码：

import os
from PIL import Image

def convert_pgm_to_png(pgm_path, png_path):
    """将 PGM 图像转换为 PNG 图像。"""
    with open(pgm_path, 'rb') as f:
        header = f.readline().decode('latin-1').strip()
        if header.startswith('P5'):
            width, height, max_gray_value = map(int, f.readline().decode('latin-1').split())
            if max_gray_value > 255:
                raise ValueError('Invalid PGM file format. Maximum gray value exceeds 255.')

            # 读取二进制图像数据，跳过注释和空格
            image_data = bytearray()
            while len(image_data) < width * height:
                byte = f.read(1)
                if byte not in (b'#', b' ', b'\t', b'\n', b'\r'):
                    image_data += byte
        else:
            raise ValueError('Invalid PGM file format. Magic number is not "P5".')

    # 创建图像并保存
    image = Image.frombytes('L', (width, height), bytes(image_data))
    image.save(png_path)

# 源目录和目标目录
source_directory = "C:\\Users\\Sara\\Desktop\\dataasets\\Newfolder\\lr(compressed)_pgm"
destination_directory = "C:\\Users\\Sara\\Desktop\\dataasets\\Newfolder\\lr\\"

# 转换所有 PGM 文件
for filename in os.listdir(source_directory):
    if filename.endswith('.pgm'):
        pgm_file = os.path.join(source_directory, filename)
        png_file = os.path.join(destination_directory, os.path.splitext(filename)[0] + '.png')
        try:
            convert_pgm_to_png(pgm_file, png_file)
        except ValueError as e:
            print(f"Error converting {pgm_file}: {str(e)}")

此代码通过逐字节读取图像数据，并跳过任何注释或空格，确保读取正确的像素值，从而解决了问题。