Solve Qt: libpng warning: iCCP: known incorrect sRGB profile

26 Jul 2021 in Qt on Qt Last modified at: 2021-07-25

libpng is more stringent about checking ICC profiles than previous versions. In Qt, if you use certain formats of PNG images, you may get a warning ‘libpng warning: iCCP: known incorrect sRGB profile’, though this will not affect the compilation.

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Why this happens?

This warning is mainly related to the format of the PNG image. In fact, to solve this warning, we just need to convert the image to a correct profile. There are many ways to solve this in both Windows and Linux.

Windows

Method 1: ImageMagick

We use ImageMagick to convert the image: ImageMagick Official

• Download the corresponding compressed package according to the platform (such as Windows x64)
• Unzip the downloaded compressed package to anywhere you want, we suppose your target path is $PATH.
• Create a new .bat file in the PNG folder, for example convert.bat.
• Edit the content of convert.bat:

@echo off
echo ImageMagick is fixing libpng warning
set fn = $PATH\convert.exe
for /f "tokens=*" %%i in ('dir/s/b *.png') do "%fn%" "%%i" -strip "%%i"
pause

• Save the convert.bat, then double click to run it.

Method 2: Photoshop

• Open the image with Photoshop.
• Click Edit on the tool bar.
• Change the image profile to “Adobe RGB (1998)”.

Method 3: QImage

QImage img;
img.load("1.png");
img.save("1.png");

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Linux

Method 1: convert

It’s the easiest way to solve the warning in Linux:

$ convert input.png output.png

If you don’t have a convert command, just install it, it is included in ImageMagick:

$ sudo apt-get install imagemagick
$ convert -version

convert also has many more excellent functions, you can resize your image like this:

$ convert -resize 1024x1024 input.png output.png

Rotate the image:

$ convert -rotate 270 input.png output.png    #clockwise rotate 270 degrees

Even add characters:

$ convert -fill COLOR -pointsize SIZE -font FONT -draw 'text X,Y "Hello, World!"' input.png output.png 

And many more…

Method 2: QImage()

QImage img;
img.load("1.png");
img.save("1.png");