fix: check if image is file path rather than b64

src/index.ts

@@ -1,6 +1,6 @@
 import * as utils from './utils.js'
 import 'whatwg-fetch'
-import { promises, createReadStream } from 'fs'
+import fs, { promises, createReadStream } from 'fs'
 import { join, resolve, dirname } from 'path'
 import { createHash } from 'crypto'
 import { homedir } from 'os'
@@ -44,7 +44,7 @@
 
   private async processStreamableRequest<T extends object>(
     endpoint: string,
     request: { stream?: boolean } & Record<string, any>,
   ): Promise<T | AsyncGenerator<T>> {
     request.stream = request.stream ?? false
     const response = await utils.post(this.fetch, `${this.config.host}/api/${endpoint}`, {
@@ -66,7 +66,7 @@
           yield message
           // message will be done in the case of chat and generate
           // message will be success in the case of a progress response (pull, push, create)
           if ((message as any).done || (message as any).status === 'success') {
             return
           }
         }
@@ -74,7 +74,7 @@
       })()
     } else {
       const message = await itr.next()
       if (!message.value.done && (message.value as any).status !== 'success') {
         throw new Error('Expected a completed response.')
       }
       return message.value
@@ -87,14 +87,17 @@
       const result = Buffer.from(image).toString('base64')
       return result
     }
-    const base64Pattern = /^[A-Za-z0-9+/]+={1,2}$/ // detect by checking for equals signs at the end
-    if (base64Pattern.test(image)) {
-      // the string is already base64 encoded
-      return image
+    try {
+      if (fs.existsSync(image)) {
+        // this is a filepath, read the file and convert it to base64
+        const fileBuffer = await promises.readFile(resolve(image))
+        return Buffer.from(fileBuffer).toString('base64')
+      }
+    } catch {
+      // continue
     }
-    // this is a filepath, read the file and convert it to base64
-    const fileBuffer = await promises.readFile(resolve(image))
-    return Buffer.from(fileBuffer).toString('base64')
+    // the string may be base64 encoded
+    return image
   }
 
   private async parseModelfile(