Saving an Image stored in BytesIO in pillow - python-imaging-library

Question

I have an image stored as BytesIO of Pillow and I need to save it to a file with some header information (containing textual attributes) that I need to add specific to my problem. I need the bytes to be represented according to some image compression format. Would that be possible? If yes, how it can be done?
I also need to store more than one image in the file.

Answer 1

Storing more than one image in a file is problematic for PNG, JPEG and the most of the common formats. One option for that is TIFF - not sure if that works for you?
Here's how you can store some additional text in a PNG at least:
#!/usr/bin/env python3
from PIL.PngImagePlugin import Image, PngInfo
# Create empty metadata and add a couple of text strings
metadata = PngInfo()
metadata.add_text("Key1:","Value1")
metadata.add_text("Key2:","Value2")
# Create red image and save with metadata embedded
im = Image.new('RGB',(64,64),'red')
im.save("result.png", pnginfo=metadata)
If you check that with pngcheck you will see:
pngcheck -7v result.png
Sample Output
File: result.png (200 bytes)
chunk IHDR at offset 0x0000c, length 13
64 x 64 image, 24-bit RGB, non-interlaced
chunk tEXt at offset 0x00025, length 12, keyword: Key1:
Value1
chunk tEXt at offset 0x0003d, length 12, keyword: Key2:
Value2
chunk IDAT at offset 0x00055, length 95
zlib: deflated, 32K window, default compression
chunk IEND at offset 0x000c0, length 0
No errors detected in result.png (5 chunks, 98.4% compression).
Here's how to save 3 images and a comment in a single TIFF file:
from PIL import Image
from PIL.TiffImagePlugin import ImageFileDirectory_v2, TiffTags
# Create a structure to hold meta-data
ifd = ImageFileDirectory_v2()
ifd[270] = 'Some Funky Comment'
ifd.tagtype[270] = TiffTags.ASCII
# Create red image and save with metadata embedded
im1 = Image.new('RGB',(50,50),'red')
im2 = Image.new('RGB',(64,64),'green')
im3 = Image.new('RGB',(80,80),'blue')
im1.save("result.tif", append_images[im2,im3], save_all=True, tiffinfo=ifd)
And check that with:
tiffinfo -v result.tif
Sample Output
TIFF Directory at offset 0x8 (8)
Image Width: 50 Image Length: 50
Bits/Sample: 8
Compression Scheme: None
Photometric Interpretation: RGB color
Samples/Pixel: 3
Rows/Strip: 50
Planar Configuration: single image plane
ImageDescription: Some Funky Comment
TIFF Directory at offset 0x1e08 (7688)
Image Width: 64 Image Length: 64
Bits/Sample: 8
Compression Scheme: None
Photometric Interpretation: RGB color
Samples/Pixel: 3
Rows/Strip: 64
Planar Configuration: single image plane
ImageDescription: Some Funky Comment
TIFF Directory at offset 0x4eb8 (20152)
Image Width: 80 Image Length: 80
Bits/Sample: 8
Compression Scheme: None
Photometric Interpretation: RGB color
Samples/Pixel: 3
Rows/Strip: 80
Planar Configuration: single image plane
ImageDescription: Some Funky Comment
You can then extract the images on the command-line with ImageMagick like this.
To extract first image:
magick result.tif[0] first.png
To extract last image:
magick result.tif[-1] last.png
To extract all three images:
magick result.tif image-%d.png
Result
-rw-r--r-- 1 mark staff 457 21 Jan 08:11 image-0.png
-rw-r--r-- 1 mark staff 458 21 Jan 08:11 image-1.png
-rw-r--r-- 1 mark staff 460 21 Jan 08:11 image-2.png
Note: Use convert in place of magick above if you are running v6 ImageMagick.
Keywords: Python, PIL, image processing, multiple images, TIF, comment, tiffinfo, IFD, PNG tEXt.