PdfDecoder

PdfDecoder.kt

import android.graphics.Bitmap
import android.graphics.pdf.PdfRenderer
import android.os.ParcelFileDescriptor
import androidx.core.graphics.drawable.toDrawable
import coil.ImageLoader
import coil.decode.DecodeResult
import coil.decode.Decoder
import coil.decode.ImageSource
import coil.fetch.SourceResult
import coil.request.Options

class PdfDecoder(
    private val source: ImageSource,
    private val options: Options,
) : Decoder {
    override suspend fun decode(): DecodeResult {
        val context = options.context
        val pdfRenderer = PdfRenderer(
            ParcelFileDescriptor.open(
                source.file().toFile(),
                ParcelFileDescriptor.MODE_READ_ONLY,
            ),
        )
        val page = pdfRenderer.openPage(0)

        // For better bitmap quality: https://stackoverflow.com/a/32327174/5285687
        // val densityDpi = context.resources.displayMetrics.densityDpi
        val bitmap = Bitmap.createBitmap(
            // densityDpi * page.width / 72,
            // densityDpi * page.height / 72,
            // Do this for now to avoid OOM.
            page.width * 2,
            page.height * 2,
            Bitmap.Config.ARGB_8888,
        )
        page.render(bitmap, null, null, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY)
        page.close()
        pdfRenderer.close()

        return DecodeResult(
            drawable = bitmap.toDrawable(context.resources),
            isSampled = false,
        )
    }

    class Factory : Decoder.Factory {
        override fun create(result: SourceResult, options: Options, imageLoader: ImageLoader): Decoder? {
            if (!isApplicable(result)) return null
            return PdfDecoder(result.source, options)
        }

        private fun isApplicable(result: SourceResult): Boolean = result.mimeType == MIME_TYPE_PDF
    }

    companion object {
        private const val MIME_TYPE_PDF = "application/pdf"
    }
}