How to change image format without writing it to disk using Python Pillow

Question

I got Pillow image that i got from the Internet:

response= urllib2.urlopen(<url to gif image>)
img = Image.open(cStringIO.StringIO(response.read()))

I want to use it with tesserocr but it wont work with GIF images.

If I save the image as PNG img.save("tmp.png") and load it img = Image.open("tmp.png") everything works.

Is there a way to do this conversion without writing to disk?

Answer 1

import io
from PIL import Image


def convertImageFormat(imgObj, outputFormat=None):
    """Convert image format
    Args:
        imgObj (Image): the Pillow Image instance
        outputFormat (str): Image format, eg: "JPEG"/"PNG"/"BMP"/"TIFF"/...
            more refer: https://pillow.readthedocs.io/en/stable/handbook/image-file-formats.html
    Returns:
        bytes, binary data of Image
    Raises:
    """
    newImgObj = imgObj
    if outputFormat and (imgObj.format != outputFormat):
        imageBytesIO = io.BytesIO()
        imgObj.save(imageBytesIO, outputFormat)
        newImgObj = Image.open(imageBytesIO)


    return newImgObj

call example:

pngImgFile = "xxx.png"
pngImgObj = Image.open(pngImgFile)
convertToFormat = "JPEG"
convertedJpgImgBytes = convertImageFormat(pngImgObj, convertToFormat)

advanced version convertImageFormat can refer my lib crifanPillow.py

import io
from PIL import Image


def convertImageFormat(imgObj, outputFormat=None, isOptimize=False, isKeepPrevValues=True):
    """Convert image format
    Args:
        imgObj (Image): the Pillow Image instance
        outputFormat (str): Image format, eg: "JPEG"/"PNG"/"BMP"/"TIFF"/...
            more refer: https://pillow.readthedocs.io/en/stable/handbook/image-file-formats.html
        isOptimize (bool): do optimize when using save to convert format
        isKeepPrevValues (bool): keep previous property values, such as: filename
    Returns:
        bytes, binary data of Image
    Raises:
    """
    newImgObj = imgObj
    if outputFormat and (imgObj.format != outputFormat):
        imageBytesIO = io.BytesIO()
        if isOptimize:
            imgObj.save(imageBytesIO, outputFormat, optimize=True)
        else:
            imgObj.save(imageBytesIO, outputFormat)
        newImgObj = Image.open(imageBytesIO)
        if isKeepPrevValues:
            if imgObj.filename:
                newImgObj.filename = imgObj.filename


    return newImgObj

Answer 2

The solution was very simple:

response= urllib2.urlopen(<url to gif image>)
img = Image.open(cStringIO.StringIO(response.read()))
img = img.convert("RGB")

Note that you need to remove the alpha channel info to make image compatible with tesserocr