Rewrite the GIF frame delay if it's below a threshold (coil-kt/coil#783) (#672)

* Rewrite the GIF frame delay if it's below a threshold (coil-kt/coil#783)

Resolve #641

* fixup! Rewrite the GIF frame delay if it's below a threshold (coil-kt/coil#783)

app/src/main/java/com/hippo/image/Image.kt

@@ -25,8 +25,15 @@ import android.graphics.ImageDecoder.Source
 import android.graphics.drawable.Animatable
 import android.graphics.drawable.BitmapDrawable
 import android.graphics.drawable.Drawable
+import coil.decode.DecodeUtils
+import coil.decode.FrameDelayRewritingSource
+import coil.decode.isGif
 import com.hippo.UriArchiveAccessor
 import com.hippo.ehviewer.EhApplication
+import okio.Buffer
+import okio.BufferedSource
+import okio.buffer
+import okio.source
 import java.io.FileInputStream
 import java.nio.ByteBuffer
 import java.nio.channels.FileChannel
@@ -80,20 +87,35 @@ class Image private constructor(source: Source, private val byteBuffer: ByteBuff
         @Throws(DecodeException::class)
         @JvmStatic
         fun decode(stream: FileInputStream): Image {
-            val src = ImageDecoder.createSource(
+            val source = stream.source().buffer()
+            val buffer = if (DecodeUtils.isGif(source)) {
+                rewriteSource(source)
+            } else {
                 stream.channel.map(
                     FileChannel.MapMode.READ_ONLY, 0,
                     stream.available().toLong()
                 )
-            )
+            }
+            val src = ImageDecoder.createSource(buffer)
             return Image(src)
         }
 
         @Throws(DecodeException::class)
         @JvmStatic
         fun decode(buffer: ByteBuffer): Image {
-            val src = ImageDecoder.createSource(buffer)
+            val source = Buffer().apply { write(buffer) }
+            val byteBuffer = if (DecodeUtils.isGif(source)) {
+                rewriteSource(source)
+            } else {
+                buffer.position(0) as ByteBuffer
+            }
+            val src = ImageDecoder.createSource(byteBuffer)
             return Image(src, buffer)
         }
+
+        private fun rewriteSource(source: BufferedSource): ByteBuffer {
+            val bufferedSource = FrameDelayRewritingSource(source).buffer()
+            return ByteBuffer.wrap(bufferedSource.use { it.readByteArray() })
+        }
     }
 }