libpng warning iCCP known incorrect sRGB profile

Question

I m trying to load a PNG image using SDL but the program doesn t work and this error appears in the console     libpng warning  iCCP  known incorrect sRGB profile   Why does this warning appear  What should I do to solve this problem

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Using IrfanView image viewer in Windows  I simply resaved the PNG image and that corrected the problem

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Libpng-1 6 is more stringent about checking ICC profiles than previous versions  You can ignore the warning   To get rid of it  remove the iCCP chunk from the PNG image   Some applications treat warnings as errors  if you are using such an application you do have to remove the chunk   You can do that with any of a variety of PNG editors such as ImageMagick s  convert in png out png   To remove the invalid iCCP chunk from all of the PNG files in a folder  directory   you can use mogrify from ImageMagick   mogrify   png   This requires that your ImageMagick was built with libpng16  You can easily check it by running   convert -list format   grep PNG   If you d like to find out which files need to be fixed instead of blindly processing all of them  you can run  pngcrush -n -q   png   where the -n means don t rewrite the files and -q means suppress most of the output except for warnings  Sorry  there s no option yet in pngcrush to suppress everything but the warnings     Binary Releases of ImageMagick are here    For Android Projects  Android Studio  navigate into res folder   For example   C   your project folder  app src main res drawable-hdpi mogrify   png

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Here is a ridiculously brute force answer   I modified the gradlew script  Here is my new exec command at the end of the file in the   exec   JAVACMD     JVM OPTS      -classpath   CLASSPATH  org gradle wrapper GradleWrapperMain          grep -v  libpng warning

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There is an easier way to fix this issue with Mac OS and Homebrew   Install homebrew if it is not installed yet   brew install libpng  pngfix --strip color --out file2 png file png   or to do it with every file in the current directory   mkdir tmp  for f in     png  do pngfix --strip color --out tmp   f    f   done   It will create a fixed copy for each png file in the current directory and put it in the the tmp subdirectory  After that  if everything is OK  you just need to override the original files   Another tip is to use the Keynote and Preview applications to create the icons  I draw them using Keynote  in the size of about 120x120 pixels  over a slide with a white background  the option to make polygons editable is great    Before exporting to Preview  I draw a rectangle around the icon  without any fill or shadow  just the outline  with the size of about 135x135  and copy everything to the clipboard  After that  you just need to open it with the Preview tool using  New from Clipboard   select a 128x128 pixels area around the icon  copy  use  New from Clipboard  again  and export it to PNG  You won t need to run the pngfix tool

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Thanks to the fantastic answer from Glenn  I used ImageMagik s  quot mogrify   png quot  functionality  However  I had images buried in sub-folders  so I used this simple Python script to apply this to all images in all sub-folders and thought it might help others  import os import subprocess  def system call args  cwd  quot   quot        print  quot Running      in      quot  format str args   cwd       subprocess call args  cwd cwd      pass  def fix image files root os curdir       for path  dirs  files in os walk os path abspath root              sys stdout write              for dir in dirs              system call  quot mogrify   png quot    quot    quot  format os path join path  dir      fix image files os curdir

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To add to Glenn s great answer  here s what I did to find which files were faulty   find   -name    png  -type f -print0   xargs          -0 pngcrush 1 8 8 w64 exe -n -q  gt  pngError txt 2 gt  amp 1   I used the find and xargs because pngcrush could not handle lots of arguments  which were returned by      png   The -print0 and -0 is required to handle file names containing spaces   Then search in the output for these lines  iCCP  Not recognizing known sRGB profile that has been edited     Installer Images installer background png      Total length of data found in critical chunks                  11286   pngcrush  iCCP  Not recognizing known sRGB profile that has been edited   And for each of those  run mogrify on it to fix them   mogrify   Installer Images installer background png   Doing this prevents having a commit changing every single png file in the repository when only a few have actually been modified  Plus it has the advantage to show exactly which files were faulty   I tested this on Windows with a Cygwin console and a zsh shell  Thanks again to Glenn who put most of the above  I m just adding an answer as it s usually easier to find than comments

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Extending the friederbluemle solution  download the pngcrush and then use the code like this if you are running it on multiple png files   path  r C   project  project  images    path to all  png images import os  png files      for dirpath  subdirs  files in os walk path       for x in files          if x endswith   png                png files append os path join dirpath  x    file  r C   Users  user  Downloads  pngcrush 1 8 9 w64 exe   pngcrush file    for name in png files      cmd   r    -ow -rem allb -reduce     format file name      os system cmd    here all the png file related to projects are in 1 folder

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Use pngcrush to remove the incorrect sRGB profile from the png file   pngcrush -ow -rem allb -reduce file png    -ow will overwrite the input file -rem allb will remove all ancillary chunks except tRNS and gAMA -reduce does lossless color-type or bit-depth reduction   In the console output you should see Removed the sRGB chunk  and possibly more messages about chunk removals  You will end up with a smaller  optimized PNG file  As the command will overwrite the original file  make sure to create a backup or use version control

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After trying a couple of the suggestions on this page I ended up using the pngcrush solution  You can use the bash script below to recursively detect and fix bad png profiles  Just pass it the full path to the directory you want to search for png files   fixpng   path to png folder    The script      bin bash  FILES   find   1  -type f -iname    png    FIXED 0 for f in  FILES  do     WARN   pngcrush -n -warn   f  2 gt  amp 1      if      WARN       PCS illuminant is not D50              WARN       known incorrect sRGB profile       then         pngcrush -s -ow -rem allb -reduce   f          FIXED    FIXED   1       fi done  echo   FIXED errors fixed

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You can also just fix this in photoshop      Open your  png file  File -  Save As and in the dialog that opens up uncheck  ICC Profile  sRGB IEC61966-2 1  Uncheck  As a Copy   Courageously save over your original  png  Move on with your life knowing that you ve removed just that little bit of evil from the world

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Solution The incorrect profile could be fixed by   Opening the image with the incorrect profile using QPixmap  load Saving the image back to the disk  already with the correct profile  using QPixmap  save  Note  This solution uses the Qt Library  Example Here is a minimal example I have written in C   in order to demonstrate how to implement the proposed solution  QPixmap pixmap  pixmap load  quot badProfileImage png quot     QFile file  quot goodProfileImage png quot    file open QIODevice  WriteOnly   pixmap save  amp file   quot PNG quot     The complete source code of a GUI application based on this example is available on GitHub  UPDATE FROM 05 12 2019  The answer was and is still valid  however there was a bug in the GUI application I have shared on GitHub  causing the output image to be empty  I have just fixed it and apologise for the inconvenience

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some background info on this      Some changes in libpng version 1 6  cause it to issue a warning or   even not work correctly with the original HP MS sRGB profile  leading   to the following stderr   libpng warning  iCCP  known incorrect sRGB   profile The old profile uses a D50 whitepoint  where D65 is standard    This profile is not uncommon  being used by Adobe Photoshop  although   it was not embedded into images by default     source  https   wiki archlinux org index php Libpng errors      Error detection in some chunks has improved  in particular the iCCP   chunk reader now does pretty complete validation of the basic format    Some bad profiles that were previously accepted are now rejected  in   particular the very old broken Microsoft HP sRGB profile  The PNG spec   requirement that only grayscale profiles may appear in images with   color type 0 or 4 and that even if the image only contains gray   pixels  only RGB profiles may appear in images with color type 2  3    or 6  is now enforced  The sRGB chunk is allowed to appear in images   with any color type     source  https   forum qt io topic 58638 solved-libpng-warning-iccp-known-incorrect-srgb-profile-drive-me-nuts 16

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I ran those two commands in the root of the project and its fixed  Basically redirect the output of the  quot find quot  command to a text file to use as your list of files to process  Then you can read that text file into  quot mogrify quot  using the  quot   quot  flag   find   png -mtime -1  gt  list txt mogrify -resize 50   list txt  That would use  quot find quot  to get all the   png images newer than 1 day and print them to a file named  quot list txt quot   Then  quot mogrify quot  reads that list  processes the images  and overwrites the originals with the resized versions  There may be minor differences in the behavior of  quot find quot  from one system to another  so you ll have to check the man page for the exact usage

[c++] libpng warning: iCCP: known incorrect sRGB profile

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