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flutterimage-compression

What is the quality in flutter_image_compress

I found that the quality compress by flutter_image_compress is not based on percentage. For example like 4.58MB image after compress with quality 50 is return 590KB. Is that mean the quality is not precentage ?

Reference : https://jtmuller5-98869.medium.com/image-compression-in-flutter-e0585ce960cc

Solution

  • The quality is not a percentage. It's passed through to the underlying JPEG compressor, so you have to look at how that underlying compressor interprets it. But even that might not be well-documented.

    For example, on iOS, the implementation divides quality by 100 to convert it to a number in the range 0.0 to 1.0 and uses the resulting fraction as the kCGImageDestinationLossyCompressionQuality parameter. Apple documents that parameter as follows:

    The desired compression quality to use when writing to an image destination. If present, the value associated with this key must be a CFNumberRef data type in the range 0.0 to 1.0. A value of 1.0 specifies to use lossless compression if destination format supports it. A value of 0.0 implies to use maximum compression.

    You might also want to read the JPEG image compression FAQ answer about quality.