added icon downloader

pipeline/03_icon_download/image.go

@@ -0,0 +1,139 @@
+package main
+
+import (
+	"bytes"
+	"encoding/binary"
+	"image"
+	_ "image/gif"
+	_ "image/jpeg"
+	_ "image/png"
+
+	_ "golang.org/x/image/webp"
+)
+
+// detectImageType checks magic bytes to determine the actual image format.
+// Returns empty string if not a recognized image format.
+func detectImageType(data []byte) string {
+	if len(data) < 4 {
+		return ""
+	}
+
+	// PNG: 89 50 4E 47
+	if data[0] == 0x89 && data[1] == 'P' && data[2] == 'N' && data[3] == 'G' {
+		return "image/png"
+	}
+
+	// GIF: GIF87a or GIF89a
+	if data[0] == 'G' && data[1] == 'I' && data[2] == 'F' {
+		return "image/gif"
+	}
+
+	// JPEG: FF D8 FF
+	if data[0] == 0xFF && data[1] == 0xD8 && data[2] == 0xFF {
+		return "image/jpeg"
+	}
+
+	// ICO: 00 00 01 00
+	if data[0] == 0x00 && data[1] == 0x00 && data[2] == 0x01 && data[3] == 0x00 {
+		return "image/x-icon"
+	}
+
+	// BMP: BM
+	if data[0] == 'B' && data[1] == 'M' {
+		return "image/bmp"
+	}
+
+	// WebP: RIFF....WEBP
+	if len(data) >= 12 && string(data[0:4]) == "RIFF" && string(data[8:12]) == "WEBP" {
+		return "image/webp"
+	}
+
+	// SVG: look for <?xml or <svg in first 256 bytes
+	if len(data) > 5 {
+		header := string(data[:min(256, len(data))])
+		if bytes.Contains([]byte(header), []byte("<svg")) || bytes.Contains([]byte(header), []byte("<?xml")) {
+			return "image/svg+xml"
+		}
+	}
+
+	return ""
+}
+
+// getImageDimensions reads image dimensions from the data.
+// Returns (0, 0) for SVG or if dimensions can't be determined.
+func getImageDimensions(data []byte, contentType string) (int, int) {
+	switch contentType {
+	case "image/svg+xml":
+		return 0, 0
+	case "image/x-icon":
+		return getICODimensions(data)
+	default:
+		// Use Go's image.DecodeConfig for standard formats
+		cfg, _, err := image.DecodeConfig(bytes.NewReader(data))
+		if err != nil {
+			return 0, 0
+		}
+		return cfg.Width, cfg.Height
+	}
+}
+
+// getICODimensions reads the ICO directory to find the largest image ≤64x64.
+// ICO format: 6-byte header + 16-byte directory entries.
+func getICODimensions(data []byte) (int, int) {
+	if len(data) < 6 {
+		return 0, 0
+	}
+
+	numImages := int(binary.LittleEndian.Uint16(data[4:6]))
+	if numImages == 0 || len(data) < 6+numImages*16 {
+		return 0, 0
+	}
+
+	bestW, bestH := 0, 0
+	for i := 0; i < numImages; i++ {
+		offset := 6 + i*16
+		w := int(data[offset])
+		h := int(data[offset+1])
+		// ICO uses 0 to mean 256
+		if w == 0 {
+			w = 256
+		}
+		if h == 0 {
+			h = 256
+		}
+
+		// Pick the largest that's ≤64x64
+		if w <= 64 && h <= 64 && w*h > bestW*bestH {
+			bestW = w
+			bestH = h
+		}
+	}
+
+	// If nothing ≤64, just report the largest
+	if bestW == 0 {
+		for i := 0; i < numImages; i++ {
+			offset := 6 + i*16
+			w := int(data[offset])
+			h := int(data[offset+1])
+			if w == 0 {
+				w = 256
+			}
+			if h == 0 {
+				h = 256
+			}
+			if w*h > bestW*bestH {
+				bestW = w
+				bestH = h
+			}
+		}
+	}
+
+	return bestW, bestH
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}