decode JPG file

[oskarko]

HI team!
Is there any way for decoding a JPG file with Spectrum just like mozjpeg does? I mean, just decode the file into rgb format, not compressing at all. Some example would be very appreciated. Thanks!

[lambdapioneer]

Hi @oskarko, absolutely!

Spectrum supports any combination of encoded/decoded images for the input and output. See: https://libspectrum.io/docs/supported_image_flows. For decoding you'll simply call spectrum.decode(...) instead of spectrum.transcode(...).

You can e.g. check the Android sample app on how to do this:

    private fun decode(): SpectrumResult {
        val optionsBuilder = DecodeOptions.Builder()
        applyModelToOptions(optionsBuilder)

        val inputStream = context.contentResolver.openInputStream(transcodeViewModel.inputImageUri!!)
        inputStream.use {
            val bitmapTarget = BitmapTarget()
            return spectrum.decode(
                    EncodedImageSource.from(inputStream),
                    bitmapTarget,
                    optionsBuilder.build(),
                    "caller_context_decode").also {
                outputBitmap = bitmapTarget.bitmap
            }
        }
    }

https://github.com/facebookincubator/spectrum/blob/master/android/sample/src/main/java/com/facebook/spectrum/sample/TranscodeAsyncTask.kt#L81-L96

[lambdapioneer]

Closing here, as I haven't heard otherwise :)