perf: eliminate Base64 from image attachment flow for instant preview

Replace eager Base64 encode/decode with URI-based approach:
- Preview loads directly from URI via Coil (zero processing on attach)
- File save, dimension read, and Base64 encode happen at send time only

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

android/core/data/src/main/java/io/picoclaw/android/core/data/local/ImageFileStorage.kt

@@ -2,27 +2,35 @@ package io.picoclaw.android.core.data.local
 
 import android.content.Context
 import android.graphics.BitmapFactory
+import android.net.Uri
 import android.util.Base64
 import io.picoclaw.android.core.domain.model.ImageData
 import java.io.File
 import java.util.UUID
 
-class ImageFileStorage(context: Context) {
+class ImageFileStorage(private val context: Context) {
 
     private val imageDir = File(context.filesDir, "chat_images").also { it.mkdirs() }
 
-    fun saveBase64ToFile(base64: String): ImageData {
+    data class SaveResult(
-        val bytes = Base64.decode(base64, Base64.DEFAULT)
+        val imageData: ImageData,
+        val base64: String
+    )
+
+    fun saveFromUri(uriString: String): SaveResult {
+        val bytes = context.contentResolver.openInputStream(Uri.parse(uriString))?.use {
+            it.readBytes()
+        } ?: error("Cannot read URI: $uriString")
+
         val file = File(imageDir, "${UUID.randomUUID()}.jpg")
         file.writeBytes(bytes)
 
         val opts = BitmapFactory.Options().apply { inJustDecodeBounds = true }
         BitmapFactory.decodeFile(file.absolutePath, opts)
 
-        return ImageData(
+        return SaveResult(
-            path = file.absolutePath,
+            imageData = ImageData(file.absolutePath, opts.outWidth, opts.outHeight),
-            width = opts.outWidth,
+            base64 = Base64.encodeToString(bytes, Base64.NO_WRAP)
-            height = opts.outHeight
         )
     }
 }

android/core/data/src/main/java/io/picoclaw/android/core/data/mapper/MessageMapper.kt

@@ -4,7 +4,6 @@ import io.picoclaw.android.core.data.local.entity.MessageEntity
 import io.picoclaw.android.core.data.remote.dto.WsIncoming
 import io.picoclaw.android.core.data.remote.dto.WsOutgoing
 import io.picoclaw.android.core.domain.model.ChatMessage
-import io.picoclaw.android.core.domain.model.ImageAttachment
 import io.picoclaw.android.core.domain.model.ImageData
 import io.picoclaw.android.core.domain.model.MessageSender
 import io.picoclaw.android.core.domain.model.MessageStatus
@@ -65,10 +64,10 @@ object MessageMapper {
         )
     }
 
-    fun toWsIncoming(text: String, images: List<ImageAttachment>): WsIncoming {
+    fun toWsIncoming(text: String, base64Images: List<String>): WsIncoming {
         return WsIncoming(
             content = text,
-            images = if (images.isNotEmpty()) images.map { it.base64 } else null
+            images = base64Images.ifEmpty { null }
         )
     }
 }

android/core/data/src/main/java/io/picoclaw/android/core/data/repository/ChatRepositoryImpl.kt

@@ -48,10 +48,10 @@ class ChatRepositoryImpl(
     }
 
     override suspend fun sendMessage(text: String, images: List<ImageAttachment>) {
-        val imageDataList = images.map { imageFileStorage.saveBase64ToFile(it.base64) }
+        val results = images.map { imageFileStorage.saveFromUri(it.uri) }
-        val entity = MessageMapper.toEntity(text, imageDataList, MessageStatus.SENDING)
+        val entity = MessageMapper.toEntity(text, results.map { it.imageData }, MessageStatus.SENDING)
         messageDao.insert(entity)
-        val wsDto = MessageMapper.toWsIncoming(text, images)
+        val wsDto = MessageMapper.toWsIncoming(text, results.map { it.base64 })
         val success = webSocketClient.send(wsDto)
         messageDao.update(entity.copy(status = if (success) MessageStatus.SENT.name else MessageStatus.FAILED.name))
     }

android/core/domain/src/main/java/io/picoclaw/android/core/domain/model/ImageAttachment.kt

@@ -1,7 +1,6 @@
 package io.picoclaw.android.core.domain.model
 
 data class ImageAttachment(
-    val uri: String? = null,
+    val uri: String,
-    val base64: String,
+    val mimeType: String = "image/jpeg"
-    val mimeType: String = "image/png"
 )

android/feature/chat/src/main/java/io/picoclaw/android/feature/chat/component/ImagePreview.kt

@@ -1,8 +1,6 @@
 package io.picoclaw.android.feature.chat.component
 
-import android.graphics.BitmapFactory
+import android.net.Uri
-import android.util.Base64
-import androidx.compose.foundation.Image
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.padding
@@ -15,13 +13,12 @@ import androidx.compose.material.icons.filled.Close
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
 import androidx.compose.runtime.Composable
-import androidx.compose.runtime.remember
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
-import androidx.compose.ui.graphics.asImageBitmap
 import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.unit.dp
+import coil3.compose.AsyncImage
 import io.picoclaw.android.core.domain.model.ImageAttachment
 
 @Composable
@@ -38,24 +35,14 @@ fun ImagePreviewRow(
     ) {
         itemsIndexed(images) { index, attachment ->
             Box {
-                val bitmap = remember(attachment.base64) {
+                AsyncImage(
-                    try {
+                    model = Uri.parse(attachment.uri),
-                        val bytes = Base64.decode(attachment.base64, Base64.DEFAULT)
-                        BitmapFactory.decodeByteArray(bytes, 0, bytes.size)?.asImageBitmap()
-                    } catch (_: Exception) {
-                        null
-                    }
-                }
-                bitmap?.let {
-                    Image(
-                        bitmap = it,
                     contentDescription = null,
                     modifier = Modifier
                         .size(64.dp)
                         .clip(RoundedCornerShape(8.dp)),
                     contentScale = ContentScale.Crop
                 )
-                }
                 IconButton(
                     onClick = { onRemove(index) },
                     modifier = Modifier

android/feature/chat/src/main/java/io/picoclaw/android/feature/chat/screen/ChatScreen.kt

@@ -1,8 +1,6 @@
 package io.picoclaw.android.feature.chat.screen
 
-import android.graphics.BitmapFactory
 import android.net.Uri
-import android.util.Base64
 import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.foundation.layout.Column
@@ -32,7 +30,6 @@ import io.picoclaw.android.feature.chat.component.ImagePreviewRow
 import io.picoclaw.android.feature.chat.component.MessageInput
 import io.picoclaw.android.feature.chat.component.MessageList
 import org.koin.androidx.compose.koinViewModel
-import java.io.ByteArrayOutputStream
 import java.io.File
 
 @OptIn(ExperimentalMaterial3Api::class)
@@ -51,16 +48,9 @@ fun ChatScreen(
     ) { success ->
         if (success) {
             cameraImageUri?.let { uri ->
-                uriToBase64(context, uri)?.let { base64 ->
                 viewModel.onEvent(
-                        ChatEvent.OnImageAdded(
+                    ChatEvent.OnImageAdded(ImageAttachment(uri = uri.toString()))
-                            ImageAttachment(
-                                uri = uri.toString(),
-                                base64 = base64
                 )
-                        )
-                    )
-                }
             }
         }
     }
@@ -69,18 +59,10 @@ fun ChatScreen(
         contract = ActivityResultContracts.GetContent()
     ) { uri ->
         uri?.let {
-            uriToBase64(context, it)?.let { base64 ->
+            val mimeType = context.contentResolver.getType(it) ?: "image/jpeg"
-                val mimeType = context.contentResolver.getType(it) ?: "image/png"
             viewModel.onEvent(
-                    ChatEvent.OnImageAdded(
+                ChatEvent.OnImageAdded(ImageAttachment(uri = it.toString(), mimeType = mimeType))
-                        ImageAttachment(
-                            uri = it.toString(),
-                            base64 = base64,
-                            mimeType = mimeType
             )
-                    )
-                )
-            }
         }
     }
 
@@ -142,16 +124,3 @@ fun ChatScreen(
         }
     }
 }
-
-private fun uriToBase64(context: android.content.Context, uri: Uri): String? {
-    return try {
-        context.contentResolver.openInputStream(uri)?.use { input ->
-            val bitmap = BitmapFactory.decodeStream(input)
-            val output = ByteArrayOutputStream()
-            bitmap.compress(android.graphics.Bitmap.CompressFormat.PNG, 100, output)
-            Base64.encodeToString(output.toByteArray(), Base64.NO_WRAP)
-        }
-    } catch (_: Exception) {
-        null
-    }
-}