first commit

backend/image_converter.go

@@ -0,0 +1,175 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"image"
+	"image/png"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+)
+
+// ConvertSVGToPNG converts an SVG file to PNG format
+// Uses ImageMagick/Inkscape if available, otherwise returns error
+func ConvertSVGToPNG(svgPath, pngPath string, width int) error {
+	// Try using ImageMagick convert command
+	if err := convertWithImageMagick(svgPath, pngPath, width); err == nil {
+		return nil
+	}
+
+	// Try using Inkscape
+	if err := convertWithInkscape(svgPath, pngPath, width); err == nil {
+		return nil
+	}
+
+	// If no converter available, copy SVG as fallback and log warning
+	return fmt.Errorf("no SVG converter available (install ImageMagick or Inkscape)")
+}
+
+// ConvertPDFToPNG converts a PDF file to PNG format
+// Uses ImageMagick/Ghostscript if available, otherwise returns error
+func ConvertPDFToPNG(pdfPath, pngPath string, width int) error {
+	// Try using ImageMagick convert command (requires Ghostscript)
+	cmd := exec.Command("convert",
+		"-background", "none",
+		"-density", "300",
+		"-resize", fmt.Sprintf("%dx%d", width, width),
+		fmt.Sprintf("%s[0]", pdfPath), // Only first page
+		pngPath,
+	)
+	
+	var stderr bytes.Buffer
+	cmd.Stderr = &stderr
+	
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("PDF conversion failed (install ImageMagick and Ghostscript): %v - %s", err, stderr.String())
+	}
+	
+	return nil
+}
+
+func convertWithImageMagick(svgPath, pngPath string, width int) error {
+	cmd := exec.Command("convert",
+		"-background", "none",
+		"-density", "300",
+		"-resize", fmt.Sprintf("%dx%d", width, width),
+		svgPath,
+		pngPath,
+	)
+	
+	var stderr bytes.Buffer
+	cmd.Stderr = &stderr
+	
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("imagemagick conversion failed: %v - %s", err, stderr.String())
+	}
+	
+	return nil
+}
+
+func convertWithInkscape(svgPath, pngPath string, width int) error {
+	cmd := exec.Command("inkscape",
+		"--export-type=png",
+		fmt.Sprintf("--export-filename=%s", pngPath),
+		fmt.Sprintf("--export-width=%d", width),
+		svgPath,
+	)
+	
+	var stderr bytes.Buffer
+	cmd.Stderr = &stderr
+	
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("inkscape conversion failed: %v - %s", err, stderr.String())
+	}
+	
+	return nil
+}
+
+// OptimizePNG optimizes a PNG file (basic implementation)
+func OptimizePNG(pngPath string) error {
+	// Open the file
+	file, err := os.Open(pngPath)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	// Decode the image
+	img, _, err := image.Decode(file)
+	if err != nil {
+		return err
+	}
+
+	// Create temp file
+	tempPath := pngPath + ".tmp"
+	tempFile, err := os.Create(tempPath)
+	if err != nil {
+		return err
+	}
+	defer tempFile.Close()
+
+	// Encode with compression
+	encoder := png.Encoder{
+		CompressionLevel: png.BestCompression,
+	}
+	
+	if err := encoder.Encode(tempFile, img); err != nil {
+		os.Remove(tempPath)
+		return err
+	}
+
+	// Replace original with optimized
+	if err := os.Rename(tempPath, pngPath); err != nil {
+		os.Remove(tempPath)
+		return err
+	}
+
+	return nil
+}
+
+// IsSVGFile checks if the file is an SVG by reading its content
+func IsSVGFile(file io.Reader) (bool, error) {
+	buf := make([]byte, 512)
+	n, err := file.Read(buf)
+	if err != nil && err != io.EOF {
+		return false, err
+	}
+
+	content := string(buf[:n])
+	return bytes.Contains([]byte(content), []byte("<svg")) ||
+		bytes.Contains([]byte(content), []byte("<?xml")), nil
+}
+
+// ValidateImageFile validates that a file is a valid SVG or PNG
+func ValidateImageFile(filePath string) (string, error) {
+	ext := filepath.Ext(filePath)
+	
+	file, err := os.Open(filePath)
+	if err != nil {
+		return "", err
+	}
+	defer file.Close()
+
+	if ext == ".svg" {
+		isSVG, err := IsSVGFile(file)
+		if err != nil {
+			return "", err
+		}
+		if !isSVG {
+			return "", fmt.Errorf("file is not a valid SVG")
+		}
+		return "svg", nil
+	}
+
+	if ext == ".png" {
+		_, err := png.Decode(file)
+		if err != nil {
+			return "", fmt.Errorf("file is not a valid PNG: %v", err)
+		}
+		return "png", nil
+	}
+
+	return "", fmt.Errorf("unsupported file format: %s", ext)
+}