WhatsApp Go MCP

package utils import ( "bytes" "fmt" "image" "image/jpeg" "io" "mime/multipart" "github.com/disintegration/imaging" ) const ( // WhatsApp group photo constraints MaxGroupPhotoSize = 100 * 1024 // 100KB GroupPhotoQuality = 80 // JPEG quality MaxGroupPhotoDimension = 640 // Max width/height in pixels ) // ProcessGroupPhoto processes an image for WhatsApp group photo requirements: // - Converts to JPEG format // - Crops to 1:1 aspect ratio (square) // - Resizes to fit within MaxGroupPhotoDimension // - Compresses to stay under MaxGroupPhotoSize func ProcessGroupPhoto(file *multipart.FileHeader) (*bytes.Buffer, error) { // Open the uploaded file src, err := file.Open() if err != nil { return nil, fmt.Errorf("failed to open uploaded file: %w", err) } defer src.Close() // Decode the image img, format, err := image.Decode(src) if err != nil { return nil, fmt.Errorf("failed to decode image: %w", err) } // Handle different input formats switch format { case "jpeg", "png", "webp": // Supported formats default: return nil, fmt.Errorf("unsupported image format: %s (only JPEG, PNG, and WebP are supported)", format) } // Crop to 1:1 aspect ratio (square) img = cropToSquare(img) // Resize if too large if img.Bounds().Dx() > MaxGroupPhotoDimension || img.Bounds().Dy() > MaxGroupPhotoDimension { img = imaging.Resize(img, MaxGroupPhotoDimension, MaxGroupPhotoDimension, imaging.Lanczos) } // Convert to JPEG with compression return compressToJPEG(img, GroupPhotoQuality) } // cropToSquare crops an image to a 1:1 aspect ratio, keeping the center func cropToSquare(img image.Image) image.Image { bounds := img.Bounds() width := bounds.Dx() height := bounds.Dy() // If already square, return as-is if width == height { return img } // Determine the size of the square (minimum of width and height) size := width if height < width { size = height } // Calculate crop position to center the square x := (width - size) / 2 y := (height - size) / 2 // Crop to square cropRect := image.Rect(x, y, x+size, y+size) return imaging.Crop(img, cropRect) } // compressToJPEG converts an image to JPEG format with specified quality // and tries to compress it to stay under the file size limit func compressToJPEG(img image.Image, quality int) (*bytes.Buffer, error) { return compressToJPEGWithDepth(img, quality, 0) } func compressToJPEGWithDepth(img image.Image, quality int, depth int) (*bytes.Buffer, error) { const maxDepth = 10 // Prevent infinite recursion if depth > maxDepth { return nil, fmt.Errorf("exceeded maximum compression attempts") } var buf bytes.Buffer // Try with initial quality err := jpeg.Encode(&buf, img, &jpeg.Options{Quality: quality}) if err != nil { return nil, fmt.Errorf("failed to encode JPEG: %w", err) } // If file is too large, reduce quality and try again if buf.Len() > MaxGroupPhotoSize && quality > 10 { return compressToJPEGWithDepth(img, quality-10, depth+1) } // If still too large even at low quality, resize the image smaller if buf.Len() > MaxGroupPhotoSize { bounds := img.Bounds() newSize := int(float64(bounds.Dx()) * 0.8) // Reduce by 20% if newSize < 100 { return nil, fmt.Errorf("image cannot be compressed enough to meet WhatsApp requirements (max %d bytes)", MaxGroupPhotoSize) } resized := imaging.Resize(img, newSize, newSize, imaging.Lanczos) return compressToJPEGWithDepth(resized, quality, depth+1) } return &buf, nil } // ValidateGroupPhotoFormat checks if the uploaded file is a supported image format func ValidateGroupPhotoFormat(file *multipart.FileHeader) error { if file == nil { return nil // Photo is optional (can be nil to remove photo) } // Check content type contentType := file.Header.Get("Content-Type") supportedTypes := map[string]bool{ "image/jpeg": true, "image/jpg": true, "image/png": true, "image/webp": true, } if contentType != "" && !supportedTypes[contentType] { return fmt.Errorf("unsupported image format: %s (supported: JPEG, PNG, WebP)", contentType) } // Check file size (before processing) if file.Size > 10*1024*1024 { // 10MB limit for input return fmt.Errorf("image file too large: %d bytes (max 10MB for processing)", file.Size) } // Try to decode the image to verify it's a valid image src, err := file.Open() if err != nil { return fmt.Errorf("failed to open uploaded file: %w", err) } defer src.Close() // Read only the first few bytes to detect format header := make([]byte, 512) _, err = src.Read(header) if err != nil && err != io.EOF { return fmt.Errorf("failed to read file header: %w", err) } // Reset to beginning if _, err := src.Seek(0, 0); err != nil { return fmt.Errorf("failed to reset file position: %w", err) } // Detect image format from header _, format, err := image.DecodeConfig(src) if err != nil { return fmt.Errorf("invalid image file: %w", err) } if format != "jpeg" && format != "png" && format != "webp" { return fmt.Errorf("unsupported image format detected: %s", format) } return nil }