1 files changed, 66 insertions, 0 deletions
diff --git a/internal/image/gemini_media.go b/internal/image/gemini_media.go
new file mode 100644
index 0000000..f04ddd3
--- /dev/null
+++ b/internal/image/gemini_media.go
@@ -0,0 +1,66 @@
+package image
+
+import (
+	"bytes"
+	"encoding/base64"
+	"fmt"
+	"image"
+	_ "image/jpeg"
+	"image/png"
+	"io"
+	"strings"
+)
+
+func encodeDataURL(imageBytes []byte, mimeType string) (string, error) {
+	if len(imageBytes) == 0 {
+		return "", fmt.Errorf("no image bytes returned")
+	}
+
+	normalizedBytes, err := normalizePNG(imageBytes, mimeType)
+	if err != nil {
+		return "", err
+	}
+
+	return geminiDataPrefix + base64.StdEncoding.EncodeToString(normalizedBytes), nil
+}
+
+func decodeDataURL(url string) (io.ReadCloser, error) {
+	header, payload, ok := strings.Cut(url, ",")
+	if !ok || !strings.HasPrefix(header, "data:") || !strings.Contains(header, ";base64") {
+		return nil, fmt.Errorf("unsupported data URI: %s", url)
+	}
+
+	data, err := base64.StdEncoding.DecodeString(payload)
+	if err != nil {
+		return nil, fmt.Errorf("decode data URI: %w", err)
+	}
+
+	return io.NopCloser(bytes.NewReader(data)), nil
+}
+
+func normalizePNG(imageBytes []byte, mimeType string) ([]byte, error) {
+	if strings.EqualFold(strings.TrimSpace(mimeType), "image/png") {
+		return append([]byte(nil), imageBytes...), nil
+	}
+
+	img, _, err := image.Decode(bytes.NewReader(imageBytes))
+	if err != nil {
+		return nil, fmt.Errorf("decode generated image: %w", err)
+	}
+
+	var buffer bytes.Buffer
+	if err := png.Encode(&buffer, img); err != nil {
+		return nil, fmt.Errorf("encode generated image as png: %w", err)
+	}
+
+	return buffer.Bytes(), nil
+}
+
+func decodedImageDimensions(imageBytes []byte) (int, int, error) {
+	cfg, _, err := image.DecodeConfig(bytes.NewReader(imageBytes))
+	if err != nil {
+		return 0, 0, fmt.Errorf("decode generated image dimensions: %w", err)
+	}
+
+	return cfg.Width, cfg.Height, nil
+}