完善生图5.0的功能

backend/internal/billing/seedream.go

@@ -8,6 +8,13 @@ import (
 
 const Seedream50ProModel = "doubao-seedream-5-0-pro-260628"
 
+const SeedreamLayerPixelThreshold = 2_610_000
+
+type SeedreamLayerImage struct {
+	Width  int
+	Height int
+}
+
 // CalculateSeedreamAmountFen applies Seedream's additive input-image price
 // before the platform markup: the first reference image is free and every
 // additional reference image costs 2 fen.
@@ -28,3 +35,26 @@ func CalculateSeedreamAmountFen(outputPriceFen int64, referenceImageCount int, m
 func IsSeedreamBillingModel(model string) bool {
 	return strings.TrimSpace(model) == Seedream50ProModel
 }
+
+// CalculateSeedreamLayerAmountFen charges every returned image independently:
+// 15 fen up to 2.61M pixels and 30 fen above that tier, followed by markup.
+func CalculateSeedreamLayerAmountFen(images []SeedreamLayerImage, markupMultiplier float64) (int64, error) {
+	if len(images) == 0 || len(images) > 17 {
+		return 0, errors.New("seedream layer output count must be between 1 and 17")
+	}
+	if math.IsNaN(markupMultiplier) || math.IsInf(markupMultiplier, 0) || markupMultiplier < 1 {
+		return 0, errors.New("seedream markup multiplier must be at least 1")
+	}
+	standardAmountFen := int64(0)
+	for _, image := range images {
+		if image.Width <= 0 || image.Height <= 0 {
+			return 0, errors.New("seedream layer output dimensions must be positive")
+		}
+		price := int64(15)
+		if int64(image.Width)*int64(image.Height) > SeedreamLayerPixelThreshold {
+			price = 30
+		}
+		standardAmountFen += price
+	}
+	return int64(math.Ceil(float64(standardAmountFen) * markupMultiplier)), nil
+}