feat(tool):add read_image tool to enable local image recognition by llms

pkg/agent/loop.go

@@ -202,6 +202,12 @@ func registerSharedTools(
 			agent.Tools.Register(sendFileTool)
 		}
 
+		// Read image tool (converts local images to base64 for LLM recognition)
+		if cfg.Tools.IsToolEnabled("read_image") {
+			readImageTool := tools.NewReadImageTool(int64(cfg.Agents.Defaults.GetMaxMediaSize()))
+			agent.Tools.Register(readImageTool)
+		}
+
 		// Skill discovery and installation tools
 		skills_enabled := cfg.Tools.IsToolEnabled("skills")
 		find_skills_enable := cfg.Tools.IsToolEnabled("find_skills")
@@ -1357,25 +1363,55 @@ func (al *AgentLoop) runLLMIteration(
 					})
 			}
 
-			// If tool returned media refs, publish them as outbound media
+			// Handle media data based on MediaDispatch type
 			if len(r.result.Media) > 0 {
-				parts := make([]bus.MediaPart, 0, len(r.result.Media))
-				for _, ref := range r.result.Media {
-					part := bus.MediaPart{Ref: ref}
-					if al.mediaStore != nil {
-						if _, meta, err := al.mediaStore.ResolveWithMeta(ref); err == nil {
-							part.Filename = meta.Filename
-							part.ContentType = meta.ContentType
-							part.Type = inferMediaType(meta.Filename, meta.ContentType)
+				switch r.result.MediaDispatch {
+				case tools.MediaDispatchToLLM:
+					// Media is base64-encoded data for LLM analysis
+					// The data will be included in the tool result message for LLM context
+					logger.DebugCF("agent", "Tool returned media for LLM analysis",
+						map[string]any{
+							"tool":        r.tc.Name,
+							"media_count": len(r.result.Media),
+						})
+
+				case tools.MediaDispatchOutbound, "":
+					// Default: media refs for external channels
+					parts := make([]bus.MediaPart, 0, len(r.result.Media))
+					for _, ref := range r.result.Media {
+						part := bus.MediaPart{Ref: ref}
+						if al.mediaStore != nil {
+							if _, meta, err := al.mediaStore.ResolveWithMeta(ref); err == nil {
+								part.Filename = meta.Filename
+								part.ContentType = meta.ContentType
+								part.Type = inferMediaType(meta.Filename, meta.ContentType)
+							}
 						}
+						parts = append(parts, part)
+					}
+					al.bus.PublishOutboundMedia(ctx, bus.OutboundMediaMessage{
+						Channel: opts.Channel,
+						ChatID:  opts.ChatID,
+						Parts:   parts,
+					})
+
+				default:
+					// Unknown dispatch type, log warning and default to outbound
+					logger.WarnCF("agent", "Unknown media dispatch type, defaulting to outbound",
+						map[string]any{
+							"tool":          r.tc.Name,
+							"dispatch_type": r.result.MediaDispatch,
+						})
+					parts := make([]bus.MediaPart, 0, len(r.result.Media))
+					for _, ref := range r.result.Media {
+						parts = append(parts, bus.MediaPart{Ref: ref})
 					}
-					parts = append(parts, part)
+					al.bus.PublishOutboundMedia(ctx, bus.OutboundMediaMessage{
+						Channel: opts.Channel,
+						ChatID:  opts.ChatID,
+						Parts:   parts,
+					})
 				}
-				al.bus.PublishOutboundMedia(ctx, bus.OutboundMediaMessage{
-					Channel: opts.Channel,
-					ChatID:  opts.ChatID,
-					Parts:   parts,
-				})
 			}
 
 			// Determine content for LLM based on tool result
@@ -1384,11 +1420,24 @@ func (al *AgentLoop) runLLMIteration(
 				contentForLLM = r.result.Err.Error()
 			}
 
+			// Build tool result message based on MediaDispatch
 			toolResultMsg := providers.Message{
 				Role:       "tool",
-				Content:    contentForLLM,
 				ToolCallID: r.tc.ID,
 			}
+
+			// Set Content and Media based on dispatch type
+			if r.result.MediaDispatch == tools.MediaDispatchToLLM && len(r.result.Media) > 0 {
+				// For LLM-bound media, mark content as [image] and include base64 data
+				toolResultMsg.Content = "[image]"
+				toolResultMsg.Media = r.result.Media
+			} else {
+				toolResultMsg.Content = contentForLLM
+				if len(r.result.Media) > 0 && r.result.MediaDispatch != tools.MediaDispatchToLLM {
+					toolResultMsg.Media = r.result.Media
+				}
+			}
+
 			messages = append(messages, toolResultMsg)
 
 			// Save tool result message to session

pkg/tools/read_image.go

@@ -0,0 +1,154 @@
+package tools
+
+import (
+	"bytes"
+	"context"
+	"encoding/base64"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/h2non/filetype"
+)
+
+// ReadImageTool reads local image files and converts them to base64-encoded data URLs.
+// This enables local images to be recognized by LLMs for image analysis tasks.
+type ReadImageTool struct {
+	maxSize int64
+}
+
+// NewReadImageTool creates a new ReadImageTool instance with the specified max file size.
+// If maxSize is 0 or negative, defaults to 10MB.
+func NewReadImageTool(maxSize int64) *ReadImageTool {
+	if maxSize <= 0 {
+		maxSize = 10 * 1024 * 1024 // Default 10MB
+	}
+	return &ReadImageTool{
+		maxSize: maxSize,
+	}
+}
+
+// Name returns the tool name.
+func (t *ReadImageTool) Name() string {
+	return "read_image"
+}
+
+// Description returns the tool description for LLM function calling.
+func (t *ReadImageTool) Description() string {
+	return "Read a local image file and convert it to base64-encoded format for LLM image recognition and analysis. " +
+		"Supports common formats: jpg, jpeg, png, gif, webp, bmp. " +
+		"The image will be sent to the LLM for content analysis."
+}
+
+// Parameters returns the JSON Schema parameter definition for the tool.
+func (t *ReadImageTool) Parameters() map[string]any {
+	return map[string]any{
+		"type": "object",
+		"properties": map[string]any{
+			"path": map[string]any{
+				"type":        "string",
+				"description": "Full path to the local image file. Supports jpg, jpeg, png, gif, webp, bmp formats.",
+			},
+		},
+		"required": []string{"path"},
+	}
+}
+
+// Execute reads the image file, validates it, and converts to base64 data URL.
+// Returns a ToolResult with Media containing the base64 data and MediaDispatch set to MediaDispatchToLLM.
+func (t *ReadImageTool) Execute(ctx context.Context, args map[string]any) *ToolResult {
+	// Parse path parameter
+	path, ok := args["path"].(string)
+	if !ok || path == "" {
+		return ErrorResult("path parameter is required and must be a string")
+	}
+
+	// Check file existence
+	info, err := os.Stat(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return ErrorResult(fmt.Sprintf("file not found: %s", path))
+		}
+		return ErrorResult(fmt.Sprintf("failed to access file: %v", err))
+	}
+
+	// Check file size
+	if info.Size() > t.maxSize {
+		return ErrorResult(fmt.Sprintf(
+			"file too large: %d bytes (max: %d bytes, ~%d MB)",
+			info.Size(), t.maxSize, t.maxSize/(1024*1024),
+		))
+	}
+
+	// Detect MIME type
+	mime, err := detectImageMIME(path)
+	if err != nil {
+		return ErrorResult(fmt.Sprintf("failed to detect file type: %v", err))
+	}
+
+	// Validate it's an image
+	if !strings.HasPrefix(mime, "image/") {
+		return ErrorResult(fmt.Sprintf("not an image file: %s (detected: %s)", path, mime))
+	}
+
+	// Encode to base64 data URL
+	dataURL, err := encodeImageToDataURL(path, mime, info, int(t.maxSize))
+	if err != nil {
+		return ErrorResult(fmt.Sprintf("failed to encode image: %v", err))
+	}
+
+	if dataURL == "" {
+		return ErrorResult("failed to encode image: empty result")
+	}
+
+	// Build result with MediaDispatch set to send to LLM
+	return &ToolResult{
+		ForLLM:        fmt.Sprintf("Image loaded successfully: %s (%s, %d bytes)", path, mime, info.Size()),
+		ForUser:       fmt.Sprintf("Image loaded: %s", path),
+		Media:         []string{dataURL},
+		MediaDispatch: MediaDispatchToLLM,
+		Silent:        false,
+		IsError:       false,
+	}
+}
+
+// detectImageMIME detects the MIME type of an image file using magic bytes.
+func detectImageMIME(path string) (string, error) {
+	kind, err := filetype.MatchFile(path)
+	if err != nil {
+		return "", err
+	}
+	if kind == filetype.Unknown {
+		return "", fmt.Errorf("unknown file type")
+	}
+	return kind.MIME.Value, nil
+}
+
+// encodeImageToDataURL encodes an image file to a base64 data URL.
+// Uses streaming encoding for memory efficiency with large files.
+func encodeImageToDataURL(localPath, mime string, info os.FileInfo, maxSize int) (string, error) {
+	if info.Size() > int64(maxSize) {
+		return "", fmt.Errorf("file too large: %d bytes", info.Size())
+	}
+
+	f, err := os.Open(localPath)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	prefix := "data:" + mime + ";base64,"
+	encodedLen := base64.StdEncoding.EncodedLen(int(info.Size()))
+	var buf bytes.Buffer
+	buf.Grow(len(prefix) + encodedLen)
+	buf.WriteString(prefix)
+
+	encoder := base64.NewEncoder(base64.StdEncoding, &buf)
+	if _, err := io.Copy(encoder, f); err != nil {
+		return "", err
+	}
+	encoder.Close()
+
+	return buf.String(), nil
+}

pkg/tools/result.go

@@ -2,6 +2,20 @@ package tools
 
 import "encoding/json"
 
+// MediaDispatchType defines how media data should be dispatched.
+// It determines whether media is sent to external channels or to the LLM for analysis.
+type MediaDispatchType string
+
+const (
+	// MediaDispatchOutbound sends media to external channels (e.g., Feishu, Discord).
+	// This is the default behavior for media store refs.
+	MediaDispatchOutbound MediaDispatchType = "OutboundMediaMessage"
+
+	// MediaDispatchToLLM sends media to the LLM for recognition and analysis.
+	// Used when media contains base64-encoded data for multimodal LLMs.
+	MediaDispatchToLLM MediaDispatchType = "SendToLLM"
+)
+
 // ToolResult represents the structured return value from tool execution.
 // It provides clear semantics for different types of results and supports
 // async operations, user-facing messages, and error handling.
@@ -31,9 +45,16 @@ type ToolResult struct {
 	// Used for internal error handling and logging.
 	Err error `json:"-"`
 
-	// Media contains media store refs produced by this tool.
-	// When non-empty, the agent will publish these as OutboundMediaMessage.
+	// Media contains media data produced by this tool.
+	// The content type depends on MediaDispatch:
+	// - MediaDispatchOutbound: media store refs (original behavior)
+	// - MediaDispatchToLLM: base64-encoded media data (e.g., "data:image/png;base64,xxx")
 	Media []string `json:"media,omitempty"`
+
+	// MediaDispatch specifies how media should be dispatched.
+	// - "OutboundMediaMessage": send to external channels (default)
+	// - "SendToLLM": inject into LLM context for analysis
+	MediaDispatch MediaDispatchType `json:"media_dispatch,omitempty"`
 }
 
 // NewToolResult creates a basic ToolResult with content for the LLM.