handle base64 image resizing for anthropic

anthropic.go

@@ -1,9 +1,15 @@
 package go_llm
 
 import (
+	"bytes"
 	"context"
+	"encoding/base64"
 	"encoding/json"
 	"fmt"
+	"image"
+	"image/gif"
+	"image/jpeg"
+	"image/png"
 	"io"
 	"log"
 	"log/slog"
@@ -77,6 +83,51 @@ func (a anthropic) requestToAnthropicRequest(req Request) anth.MessagesRequest {
 				}
 
 				if img.Base64 != "" {
+
+					// Anthropic models expect images to be < 5MiB in size
+					raw, err := base64.StdEncoding.DecodeString(img.Base64)
+
+					if err != nil {
+						continue
+					}
+
+					// Check if image size exceeds 5MiB (5242880 bytes)
+					if len(raw) >= 5242880 {
+						// Decode the image
+						imgData, format, err := image.Decode(bytes.NewReader(raw))
+						if err != nil {
+							log.Println("failed to decode image", err)
+							continue
+						}
+
+						var buf bytes.Buffer
+
+						switch format {
+						case "jpeg", "jpg":
+							err = jpeg.Encode(&buf, imgData, &jpeg.Options{Quality: 60})
+						case "png":
+							// For PNG, use a higher compression level
+							enc := &png.Encoder{
+								CompressionLevel: png.BestCompression,
+							}
+							err = enc.Encode(&buf, imgData)
+						case "gif":
+							err = gif.Encode(&buf, imgData, &gif.Options{
+								NumColors: 128,
+							})
+						default:
+							continue
+						}
+
+						if err != nil {
+							log.Println("failed to encode image", err)
+							continue
+						}
+
+						// Update the base64 string
+						img.Base64 = base64.StdEncoding.EncodeToString(buf.Bytes())
+					}
+
 					m.Content = append(m.Content, anth.NewImageMessageContent(
 						anth.NewMessageContentSource(
 							anth.MessagesContentSourceTypeBase64,