Getting "cannot write mode P as JPEG" while operating on JPG image

You need to convert the image to RGB mode.

Image.open('old.jpeg').convert('RGB').save('new.jpeg')

This answer is quite old, however, I thought I will put a better way to do the same by checking for the mode before doing the conversion:

if img.mode != 'RGB':    img = img.convert('RGB')

This is required to save your image in JPEG format.

summary 1 and 2:

• backgroud
  • JPG not support alpha = transparency
  • RGBA, P has alpha = transparency
    • RGBA= Red Green Blue Alpha
• result
  • cannot write mode RGBA as JPEG
  • cannot write mode P as JPEG
• solution
  • before save to JPG, discard alpha = transparency
    • such as: convert Image to RGB
  • then save to JPG
• your code

if im.mode == "JPEG":    im.save("xxx.jpg")    # in most case, resulting jpg file is resized small oneelif rgba_or_p_im.mode in ["RGBA", "P"]:    rgb_im = rgba_or_p_im.convert("RGB")    rgb_im.save("xxx.jpg")    # some minor case, resulting jpg file is larger one, should meet your expectation

• do more for you:

about resize imgae file, I have implement a function, for your refer:

from PIL import Image, ImageDrawcfgDefaultImageResample = Image.BICUBIC # Image.LANCZOSdef resizeImage(inputImage,                newSize,                resample=cfgDefaultImageResample,                outputFormat=None,                outputImageFile=None                ):    """        resize input image        resize normally means become smaller, reduce size    :param inputImage: image file object(fp) / filename / binary bytes    :param newSize: (width, height)    :param resample: PIL.Image.NEAREST, PIL.Image.BILINEAR, PIL.Image.BICUBIC, or PIL.Image.LANCZOS        https://pillow.readthedocs.io/en/stable/reference/Image.html#PIL.Image.Image.thumbnail    :param outputFormat: PNG/JPEG/BMP/GIF/TIFF/WebP/..., more refer:        https://pillow.readthedocs.io/en/stable/handbook/image-file-formats.html        if input image is filename with suffix, can omit this -> will infer from filename suffix    :param outputImageFile: output image file filename    :return:        input image file filename: output resized image to outputImageFile        input image binary bytes: resized image binary bytes    """    openableImage = None    if isinstance(inputImage, str):        openableImage = inputImage    elif CommonUtils.isFileObject(inputImage):        openableImage = inputImage    elif isinstance(inputImage, bytes):        inputImageLen = len(inputImage)        openableImage = io.BytesIO(inputImage)    if openableImage:        imageFile = Image.open(openableImage)    elif isinstance(inputImage, Image.Image):        imageFile = inputImage    # <PIL.PngImagePlugin.PngImageFile image mode=RGBA size=3543x3543 at 0x1065F7A20>    imageFile.thumbnail(newSize, resample)    if outputImageFile:        # save to file        imageFile.save(outputImageFile)        imageFile.close()    else:        # save and return binary byte        imageOutput = io.BytesIO()        # imageFile.save(imageOutput)        outputImageFormat = None        if outputFormat:            outputImageFormat = outputFormat        elif imageFile.format:            outputImageFormat = imageFile.format        imageFile.save(imageOutput, outputImageFormat)        imageFile.close()        compressedImageBytes = imageOutput.getvalue()        compressedImageLen = len(compressedImageBytes)        compressRatio = float(compressedImageLen)/float(inputImageLen)        print("%s -> %s, resize ratio: %d%%" % (inputImageLen, compressedImageLen, int(compressRatio * 100)))        return compressedImageBytes

latest code can found here:

https://github.com/crifan/crifanLibPython/blob/master/python3/crifanLib/thirdParty/crifanPillow.py