How do I resize an image using PIL and maintain its aspect ratio

Question

Is there an obvious way to do this that I m missing   I m just trying to make thumbnails

User · Answer

Have updated the answer above by  tomvon   from PIL import Image  img   Image open image path   width  height   img size  2   if height  gt  width      baseheight   64     hpercent    baseheight float img size 1        wsize   int  float img size 0   float hpercent        img   img resize  wsize  baseheight   Image ANTIALIAS      img save  resized jpg   else      basewidth   64     wpercent    basewidth float img size 0        hsize   int  float img size 1   float wpercent        img   img resize  basewidth hsize   Image ANTIALIAS      img save  resized jpg

User · Answer

I was trying to resize some images for a slideshow video and because of that  I wanted not just one max dimension  but a max width and a max height  the size of the video frame   And there was always the possibility of a portrait video    The Image thumbnail method was promising  but I could not make it upscale a smaller image   So after I couldn t find an obvious way to do that here  or at some other places   I wrote this function and put it here for the ones to come   from PIL import Image  def get resized img img path  video size       img   Image open img path      width  height   video size    these are the MAX dimensions     video ratio   width   height     img ratio   img size 0    img size 1      if video ratio  gt   1     the video is wide         if img ratio  lt   video ratio     image is not wide enough             width new   int height   img ratio              size new   width new  height         else     image is wider than video             height new   int width   img ratio              size new   width  height new     else     the video is tall         if img ratio  gt   video ratio     image is not tall enough             height new   int width   img ratio              size new   width  height new         else     image is taller than video             width new   int height   img ratio              size new   width new  height     return img resize size new  resample Image LANCZOS

User · Answer

I was trying to resize some images for a slideshow video and because of that  I wanted not just one max dimension  but a max width and a max height  the size of the video frame   And there was always the possibility of a portrait video    The Image thumbnail method was promising  but I could not make it upscale a smaller image   So after I couldn t find an obvious way to do that here  or at some other places   I wrote this function and put it here for the ones to come   from PIL import Image  def get resized img img path  video size       img   Image open img path      width  height   video size    these are the MAX dimensions     video ratio   width   height     img ratio   img size 0    img size 1      if video ratio  gt   1     the video is wide         if img ratio  lt   video ratio     image is not wide enough             width new   int height   img ratio              size new   width new  height         else     image is wider than video             height new   int width   img ratio              size new   width  height new     else     the video is tall         if img ratio  gt   video ratio     image is not tall enough             height new   int width   img ratio              size new   width  height new         else     image is taller than video             width new   int height   img ratio              size new   width new  height     return img resize size new  resample Image LANCZOS

User · Answer

Define a maximum size  Then  compute a resize ratio by taking min maxwidth width  maxheight height    The proper size is oldsize ratio   There is of course also a library method to do this  the method Image thumbnail  Below is an  edited  example from the PIL documentation   import os  sys import Image  size   128  128  for infile in sys argv 1        outfile   os path splitext infile  0      thumbnail      if infile    outfile          try              im   Image open infile              im thumbnail size  Image ANTIALIAS              im save outfile   JPEG           except IOError              print  cannot create thumbnail for   s     infile

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I resizeed the image in such a way and it s working very well  from io import BytesIO from django core files uploadedfile import InMemoryUploadedFile import os  sys from PIL import Image   def imageResize image       outputIoStream   BytesIO       imageTemproaryResized   imageTemproary resize   1920 1080   Image ANTIALIAS       imageTemproaryResized save outputIoStream   format  PNG   quality  10        outputIoStream seek 0      uploadedImage   InMemoryUploadedFile outputIoStream  ImageField     s jpg    image name split      0    image jpeg   sys getsizeof outputIoStream   None          For upload local folder     fs   FileSystemStorage       filename   fs save uploadedImage name  uploadedImage

User · Answer

Based in  tomvon  I finished using the following  pick your case    a  Resizing height  I know the new width  so I need the new height   new width    680 new height   new width   height   width    b  Resizing width  I know the new height  so I need the new width   new height   680 new width    new height   width   height   Then just   img   img resize  new width  new height   Image ANTIALIAS

User · Answer

Define a maximum size  Then  compute a resize ratio by taking min maxwidth width  maxheight height    The proper size is oldsize ratio   There is of course also a library method to do this  the method Image thumbnail  Below is an  edited  example from the PIL documentation   import os  sys import Image  size   128  128  for infile in sys argv 1        outfile   os path splitext infile  0      thumbnail      if infile    outfile          try              im   Image open infile              im thumbnail size  Image ANTIALIAS              im save outfile   JPEG           except IOError              print  cannot create thumbnail for   s     infile

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import cv2 from skimage import data  import matplotlib pyplot as plt from skimage util import img as ubyte from skimage import io filename  abc png  image plt imread filename  im cv2 imread  abc png   print im shape  im resize 300 300  print im shape  plt imshow image

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I will also add a version of the resize that keeps the aspect ratio fixed  In this case  it will adjust the height to match the width of the new image  based on the initial aspect ratio  asp rat  which is float       But  to adjust the width to the height  instead  you just need to comment one line and uncomment the other in the else loop  You will see  where   You do not need the semicolons      I keep them just to remind myself of syntax of languages I use more often   from PIL import Image  img path    filename png   img   Image open img path         puts our image to the buffer of the PIL Image object  width  height   img size  asp rat   width height     Enter new width  in pixels  new width   50     Enter new height  in pixels  new height   54   new rat   new width new height   if  new rat    asp rat       img   img resize  new width  new height   Image ANTIALIAS       adjusts the height to match the width   NOTE  if you want to adjust the width to the height  instead - gt     uncomment the second line  new width  and comment the first one  new height  else      new height   round new width   asp rat        new width   round new height   asp rat       img   img resize  new width  new height   Image ANTIALIAS      usage  resize  x y   resample    resample filter - gt  PIL Image BILINEAR  PIL Image NEAREST  default   PIL Image BICUBIC  etc     https   pillow readthedocs io en 3 1 x reference Image html PIL Image Image resize    Enter the name under which you would like to save the new image img save  outputname png      And  it is done  I tried to document it as much as I can  so it is clear    I hope it might be helpful to someone out there

User · Answer

A simple method for keeping constrained ratios and passing a max width   height  Not the prettiest but gets the job done and is easy to understand   def resize img path  max px size  output folder       with Image open img path  as img          width 0  height 0   img size         out f name   os path split img path  -1          out f path   os path join output folder  out f name           if max  width 0  height 0    lt   max px size              print  writing    to disk  no change from original   format out f path               img save out f path              return          if width 0  gt  height 0              wpercent   max px size   float width 0              hsize   int float height 0    float wpercent               img   img resize  max px size  hsize   Image ANTIALIAS              print  writing    to disk  format out f path               img save out f path              return          if width 0  lt  height 0              hpercent   max px size   float height 0              wsize   int float width 0    float hpercent               img   img resize  max px size  wsize   Image ANTIALIAS              print  writing    to disk  format out f path               img save out f path              return   Here s a python script that uses this function to run batch image resizing

User · Answer

If you don t want   don t have a need to open image with Pillow  use this   from PIL import Image  new img arr   numpy array Image fromarray img arr  resize  new width  new height   Image ANTIALIAS

User · Answer

I also recommend using PIL s thumbnail method  because it removes all the ratio hassles from you   One important hint  though  Replace  im thumbnail size    with  im thumbnail size Image ANTIALIAS    by default  PIL uses the Image NEAREST filter for resizing which results in good performance  but poor quality

User · Answer

Just updating this question with a more modern wrapper This library wraps Pillow  a fork of PIL  https   pypi org project python-resize-image   Allowing you to do something like this  -  from PIL import Image from resizeimage import resizeimage  fd img   open  test-image jpeg    r   img   Image open fd img  img   resizeimage resize width img  200  img save  test-image-width jpeg   img format  fd img close     Heaps more examples in the above link

User · Answer

I will also add a version of the resize that keeps the aspect ratio fixed  In this case  it will adjust the height to match the width of the new image  based on the initial aspect ratio  asp rat  which is float       But  to adjust the width to the height  instead  you just need to comment one line and uncomment the other in the else loop  You will see  where   You do not need the semicolons      I keep them just to remind myself of syntax of languages I use more often   from PIL import Image  img path    filename png   img   Image open img path         puts our image to the buffer of the PIL Image object  width  height   img size  asp rat   width height     Enter new width  in pixels  new width   50     Enter new height  in pixels  new height   54   new rat   new width new height   if  new rat    asp rat       img   img resize  new width  new height   Image ANTIALIAS       adjusts the height to match the width   NOTE  if you want to adjust the width to the height  instead - gt     uncomment the second line  new width  and comment the first one  new height  else      new height   round new width   asp rat        new width   round new height   asp rat       img   img resize  new width  new height   Image ANTIALIAS      usage  resize  x y   resample    resample filter - gt  PIL Image BILINEAR  PIL Image NEAREST  default   PIL Image BICUBIC  etc     https   pillow readthedocs io en 3 1 x reference Image html PIL Image Image resize    Enter the name under which you would like to save the new image img save  outputname png      And  it is done  I tried to document it as much as I can  so it is clear    I hope it might be helpful to someone out there

User · Answer

from PIL import Image  img   Image open   your image path image jpg     image extension   png   jpg new width    200 new height   300 img   img resize  new width  new height   Image ANTIALIAS  img save  output image name png     format may what you want   png   jpg    gif

User · Answer

Define a maximum size  Then  compute a resize ratio by taking min maxwidth width  maxheight height    The proper size is oldsize ratio   There is of course also a library method to do this  the method Image thumbnail  Below is an  edited  example from the PIL documentation   import os  sys import Image  size   128  128  for infile in sys argv 1        outfile   os path splitext infile  0      thumbnail      if infile    outfile          try              im   Image open infile              im thumbnail size  Image ANTIALIAS              im save outfile   JPEG           except IOError              print  cannot create thumbnail for   s     infile

User · Answer

Based in  tomvon  I finished using the following  pick your case    a  Resizing height  I know the new width  so I need the new height   new width    680 new height   new width   height   width    b  Resizing width  I know the new height  so I need the new width   new height   680 new width    new height   width   height   Then just   img   img resize  new width  new height   Image ANTIALIAS

User · Answer

PIL already has the option to crop an image  img   ImageOps fit img  size  Image ANTIALIAS

User · Answer

You can combine PIL s Image thumbnail with sys maxsize if your resize limit is only on one dimension  width or height   For instance  if you want to resize an image so that its height is no more than 100px  while keeping aspect ratio  you can do something like this  import sys from PIL import Image  image thumbnail  sys maxsize  100   Image ANTIALIAS   Keep in mind that Image thumbnail will resize the image in place  which is different from Image resize that instead returns the resized image without changing the original one

User · Answer

The following script creates nice thumbnails of all JPEG images preserving aspect ratios with 128x128 max resolution  from PIL import Image img   Image open  quot D   Pictures  John jpg quot   img thumbnail  680 680   img save  quot D   Pictures  John resize jpg quot

User · Answer

If you are trying to maintain the same aspect ratio  then wouldn t you resize by some percentage of the original size   For example  half the original size  half   0 5 out   im resize   int half   s  for s in im size

User · Answer

This script will resize an image  somepic jpg  using PIL  Python Imaging Library  to a width of 300 pixels and a height proportional to the new width  It does this by determining what percentage 300 pixels is of the original width  img size 0   and then multiplying the original height  img size 1   by that percentage  Change  quot basewidth quot  to any other number to change the default width of your images  from PIL import Image  basewidth   300 img   Image open  somepic jpg   wpercent    basewidth float img size 0    hsize   int  float img size 1   float wpercent    img   img resize  basewidth hsize   Image ANTIALIAS  img save  somepic jpg

User · Answer

If you are trying to maintain the same aspect ratio  then wouldn t you resize by some percentage of the original size   For example  half the original size  half   0 5 out   im resize   int half   s  for s in im size

User · Answer

You can resize image by below code   From PIL import Image img Image open  Filename jpg     paste image in python folder print img size    new img img resize  400 400   new img save  new filename jpg

User · Answer

PIL already has the option to crop an image  img   ImageOps fit img  size  Image ANTIALIAS

User · Answer

I also recommend using PIL s thumbnail method  because it removes all the ratio hassles from you   One important hint  though  Replace  im thumbnail size    with  im thumbnail size Image ANTIALIAS    by default  PIL uses the Image NEAREST filter for resizing which results in good performance  but poor quality

User · Answer

This script will resize an image  somepic jpg  using PIL  Python Imaging Library  to a width of 300 pixels and a height proportional to the new width  It does this by determining what percentage 300 pixels is of the original width  img size 0   and then multiplying the original height  img size 1   by that percentage  Change  quot basewidth quot  to any other number to change the default width of your images  from PIL import Image  basewidth   300 img   Image open  somepic jpg   wpercent    basewidth float img size 0    hsize   int  float img size 1   float wpercent    img   img resize  basewidth hsize   Image ANTIALIAS  img save  somepic jpg

User · Answer

If you are trying to maintain the same aspect ratio  then wouldn t you resize by some percentage of the original size   For example  half the original size  half   0 5 out   im resize   int half   s  for s in im size

User · Answer

You can combine PIL s Image thumbnail with sys maxsize if your resize limit is only on one dimension  width or height   For instance  if you want to resize an image so that its height is no more than 100px  while keeping aspect ratio  you can do something like this  import sys from PIL import Image  image thumbnail  sys maxsize  100   Image ANTIALIAS   Keep in mind that Image thumbnail will resize the image in place  which is different from Image resize that instead returns the resized image without changing the original one

User · Answer

from PIL import Image from resizeimage import resizeimage  def resize file in file  out file  size       with open in file  as fd          image   resizeimage resize thumbnail Image open fd   size      image save out file      image close    resize file  foo tif    foo small jpg    256  256     I use this library   pip install python-resize-image

User · Answer

This script will resize an image  somepic jpg  using PIL  Python Imaging Library  to a width of 300 pixels and a height proportional to the new width  It does this by determining what percentage 300 pixels is of the original width  img size 0   and then multiplying the original height  img size 1   by that percentage  Change  quot basewidth quot  to any other number to change the default width of your images  from PIL import Image  basewidth   300 img   Image open  somepic jpg   wpercent    basewidth float img size 0    hsize   int  float img size 1   float wpercent    img   img resize  basewidth hsize   Image ANTIALIAS  img save  somepic jpg

User · Answer

This script will resize an image  somepic jpg  using PIL  Python Imaging Library  to a width of 300 pixels and a height proportional to the new width  It does this by determining what percentage 300 pixels is of the original width  img size 0   and then multiplying the original height  img size 1   by that percentage  Change  quot basewidth quot  to any other number to change the default width of your images  from PIL import Image  basewidth   300 img   Image open  somepic jpg   wpercent    basewidth float img size 0    hsize   int  float img size 1   float wpercent    img   img resize  basewidth hsize   Image ANTIALIAS  img save  somepic jpg

User · Answer

Have updated the answer above by  tomvon   from PIL import Image  img   Image open image path   width  height   img size  2   if height  gt  width      baseheight   64     hpercent    baseheight float img size 1        wsize   int  float img size 0   float hpercent        img   img resize  wsize  baseheight   Image ANTIALIAS      img save  resized jpg   else      basewidth   64     wpercent    basewidth float img size 0        hsize   int  float img size 1   float wpercent        img   img resize  basewidth hsize   Image ANTIALIAS      img save  resized jpg

User · Answer

from PIL import Image  img   Image open   your image path image jpg     image extension   png   jpg new width    200 new height   300 img   img resize  new width  new height   Image ANTIALIAS  img save  output image name png     format may what you want   png   jpg    gif

User · Answer

If you don t want   don t have a need to open image with Pillow  use this   from PIL import Image  new img arr   numpy array Image fromarray img arr  resize  new width  new height   Image ANTIALIAS

User · Answer

My ugly example   Function get file like   pic 0-9a-z   extension    resize them to 120x120  moves section to center and save to  ico 0-9a-z   extension    works with portrait and landscape   def imageResize filepath       from PIL import Image     file dir os path split filepath      img   Image open filepath       if img size 0   gt  img size 1           aspect   img size 1  120         new size    img size 0  aspect  120      else          aspect   img size 0  120         new size    120  img size 1  aspect      img resize new size  save file dir 0    ico  file dir 1  3        img   Image open file dir 0    ico  file dir 1  3         if img size 0   gt  img size 1           new img   img crop                   img size 0  -120  2               0              120    img size 0  -120  2               120                 else          new img   img crop                0                 img size 1  -120  2               120              120    img size 1  -120  2                   new img save file dir 0    ico  file dir 1  3

User · Answer

The following script creates nice thumbnails of all JPEG images preserving aspect ratios with 128x128 max resolution  from PIL import Image img   Image open  quot D   Pictures  John jpg quot   img thumbnail  680 680   img save  quot D   Pictures  John resize jpg quot

User · Answer

A simple method for keeping constrained ratios and passing a max width   height  Not the prettiest but gets the job done and is easy to understand   def resize img path  max px size  output folder       with Image open img path  as img          width 0  height 0   img size         out f name   os path split img path  -1          out f path   os path join output folder  out f name           if max  width 0  height 0    lt   max px size              print  writing    to disk  no change from original   format out f path               img save out f path              return          if width 0  gt  height 0              wpercent   max px size   float width 0              hsize   int float height 0    float wpercent               img   img resize  max px size  hsize   Image ANTIALIAS              print  writing    to disk  format out f path               img save out f path              return          if width 0  lt  height 0              hpercent   max px size   float height 0              wsize   int float width 0    float hpercent               img   img resize  max px size  wsize   Image ANTIALIAS              print  writing    to disk  format out f path               img save out f path              return   Here s a python script that uses this function to run batch image resizing

User · Answer

Open your image file   from PIL import Image im   Image open  image png     Use PIL Image resize size  resample 0  method  where you substitute  width  height  of your image for the size 2-tuple   This will display your image at original size   display im resize  int im size 0   int im size 1     0      This will display your image at 1 2 the size   display im resize  int im size 0  2  int im size 1  2    0      This will display your image at 1 3 the size   display im resize  int im size 0  3  int im size 1  3    0      This will display your image at 1 4 the size   display im resize  int im size 0  4  int im size 1  4    0      etc etc

User · Answer

Just updating this question with a more modern wrapper This library wraps Pillow  a fork of PIL  https   pypi org project python-resize-image   Allowing you to do something like this  -  from PIL import Image from resizeimage import resizeimage  fd img   open  test-image jpeg    r   img   Image open fd img  img   resizeimage resize width img  200  img save  test-image-width jpeg   img format  fd img close     Heaps more examples in the above link

User · Answer

If you are trying to maintain the same aspect ratio  then wouldn t you resize by some percentage of the original size   For example  half the original size  half   0 5 out   im resize   int half   s  for s in im size

User · Answer

I resizeed the image in such a way and it s working very well  from io import BytesIO from django core files uploadedfile import InMemoryUploadedFile import os  sys from PIL import Image   def imageResize image       outputIoStream   BytesIO       imageTemproaryResized   imageTemproary resize   1920 1080   Image ANTIALIAS       imageTemproaryResized save outputIoStream   format  PNG   quality  10        outputIoStream seek 0      uploadedImage   InMemoryUploadedFile outputIoStream  ImageField     s jpg    image name split      0    image jpeg   sys getsizeof outputIoStream   None          For upload local folder     fs   FileSystemStorage       filename   fs save uploadedImage name  uploadedImage

User · Answer

Define a maximum size  Then  compute a resize ratio by taking min maxwidth width  maxheight height    The proper size is oldsize ratio   There is of course also a library method to do this  the method Image thumbnail  Below is an  edited  example from the PIL documentation   import os  sys import Image  size   128  128  for infile in sys argv 1        outfile   os path splitext infile  0      thumbnail      if infile    outfile          try              im   Image open infile              im thumbnail size  Image ANTIALIAS              im save outfile   JPEG           except IOError              print  cannot create thumbnail for   s     infile

User · Answer

from PIL import Image from resizeimage import resizeimage  def resize file in file  out file  size       with open in file  as fd          image   resizeimage resize thumbnail Image open fd   size      image save out file      image close    resize file  foo tif    foo small jpg    256  256     I use this library   pip install python-resize-image

User · Answer

Open your image file   from PIL import Image im   Image open  image png     Use PIL Image resize size  resample 0  method  where you substitute  width  height  of your image for the size 2-tuple   This will display your image at original size   display im resize  int im size 0   int im size 1     0      This will display your image at 1 2 the size   display im resize  int im size 0  2  int im size 1  2    0      This will display your image at 1 3 the size   display im resize  int im size 0  3  int im size 1  3    0      This will display your image at 1 4 the size   display im resize  int im size 0  4  int im size 1  4    0      etc etc

User · Answer

My ugly example   Function get file like   pic 0-9a-z   extension    resize them to 120x120  moves section to center and save to  ico 0-9a-z   extension    works with portrait and landscape   def imageResize filepath       from PIL import Image     file dir os path split filepath      img   Image open filepath       if img size 0   gt  img size 1           aspect   img size 1  120         new size    img size 0  aspect  120      else          aspect   img size 0  120         new size    120  img size 1  aspect      img resize new size  save file dir 0    ico  file dir 1  3        img   Image open file dir 0    ico  file dir 1  3         if img size 0   gt  img size 1           new img   img crop                   img size 0  -120  2               0              120    img size 0  -120  2               120                 else          new img   img crop                0                 img size 1  -120  2               120              120    img size 1  -120  2                   new img save file dir 0    ico  file dir 1  3

User · Answer

import cv2 from skimage import data  import matplotlib pyplot as plt from skimage util import img as ubyte from skimage import io filename  abc png  image plt imread filename  im cv2 imread  abc png   print im shape  im resize 300 300  print im shape  plt imshow image

User · Answer

You can resize image by below code   From PIL import Image img Image open  Filename jpg     paste image in python folder print img size    new img img resize  400 400   new img save  new filename jpg

[python] How do I resize an image using PIL and maintain its aspect ratio?

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