moteva/server/internal/application/layer_separation.go

package application

import (
	"bytes"
	"context"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"image"
	"image/color"
	"image/draw"
	"image/png"
	"math"
	"sort"
	"strconv"
	"strings"
	"time"

	"img_infinite_canvas/internal/domain/design"
)

const (
	layerSeparationForegroundLabel = "fg_image"
	layerSeparationBackgroundLabel = "bg_image"
	layerSeparationTextLabel       = "text_render_data"
)

type layerSeparationResult struct {
	CanvasWidth    int64
	CanvasHeight   int64
	BackgroundID   string
	BackgroundURL  string
	Foregrounds    []layerSeparationForeground
	TextExtraction design.TextExtraction
	Artifacts      []design.GeneratorTaskArtifact
}

type layerSeparationForeground struct {
	ID     string
	URL    string
	BBox   []int64
	Width  int64
	Height int64
	Mask   *image.Alpha
	Rect   image.Rectangle
}

type layerSeparationForegroundCandidate struct {
	BBox   []int64
	Width  int64
	Height int64
	Mask   *image.Alpha
	Rect   image.Rectangle
	Image  image.Image
}

func (s *DesignService) completeLayerSeparationGeneration(ctx context.Context, projectID string, threadID string, target design.Node, req design.NodeActionRequest) error {
	resultNodeID := nodeActionResultNodeID(target, req)
	if err := s.addGenerationStep(ctx, projectID, threadID, "tool", "图层分离", "正在拆分底图、前景元素和可编辑文字层。"); err != nil {
		return s.markNodeActionFailed(detachedUserContext(ctx), projectID, threadID, resultNodeID, err)
	}

	resultTarget := target
	resultTarget.ID = resultNodeID
	result, err := s.createLayerSeparationResult(ctx, projectID, resultTarget, req)
	if err != nil {
		return s.markNodeActionFailed(detachedUserContext(ctx), projectID, threadID, resultNodeID, err)
	}

	project, err := s.repo.Get(ctx, projectID)
	if err != nil {
		return err
	}
	nodeIndex := findNodeIndex(project.Nodes, resultNodeID)
	if nodeIndex < 0 {
		project.Nodes = append(project.Nodes, newLayerSeparationPlaceholder(target))
		nodeIndex = len(project.Nodes) - 1
		project.Nodes[nodeIndex].ID = resultNodeID
	}

	frameNode := project.Nodes[nodeIndex]
	if frameNode.Width <= 0 {
		frameNode.Width = float64(result.CanvasWidth)
	}
	if frameNode.Height <= 0 {
		frameNode.Height = float64(result.CanvasHeight)
	}
	frameNode.Type = design.NodeTypeFrame
	frameNode.Title = "Frame"
	frameNode.Content = ""
	frameNode.Tone = "frame"
	frameNode.Status = "success"
	frameNode.ParentID = ""
	frameNode.LayerRole = "manual-frame"
	frameNode.FillColor = "transparent"
	frameNode.StrokeColor = "#C7C7C7"
	frameNode.StrokeWidth = 1
	frameNode.StrokeStyle = "solid"
	frameNode.MockupSurface = design.MockupSurface{}
	frameNode.MockupModel = design.MockupModel{}
	frameNode.MockupSourceContent = ""

	now := s.now()
	backgroundNode := newLayerSeparationBackgroundNode(frameNode, result)
	foregroundNodes := newForegroundImageLayers(frameNode, result.Foregrounds, result.CanvasWidth, result.CanvasHeight)
	editableTextNodes := newEditableTextLayers(frameNode, result.TextExtraction)
	replacementNodes := make([]design.Node, 0, len(foregroundNodes)+len(editableTextNodes)+2)
	replacementNodes = append(replacementNodes, backgroundNode, frameNode)
	replacementNodes = append(replacementNodes, foregroundNodes...)
	replacementNodes = append(replacementNodes, editableTextNodes...)
	project.Nodes = append(project.Nodes[:nodeIndex], append(replacementNodes, project.Nodes[nodeIndex+1:]...)...)
	project.Messages = append(project.Messages, layerSeparationArtifactsMessage(threadID, result.Artifacts, now.Add(-time.Millisecond)))
	project.Messages = append(project.Messages, design.Message{
		ID:        newID(),
		Role:      "assistant",
		Type:      "assistant",
		Title:     nodeActionDoneTitle(req.Action),
		Content:   nodeActionDoneContent(req.Action, req.Prompt),
		ThreadID:  threadID,
		ActionID:  threadID,
		StepID:    newID(),
		Name:      "canvas_action",
		ToolHint:  "canvas_action",
		Status:    "success",
		CreatedAt: now,
	})
	project.Connections = nil
	project.Status = projectStatusAfterCanvasTask(project.Nodes, design.StatusReady)
	project.UpdatedAt = now
	project = s.refreshCanvasSnapshot(project, now)

	return s.repo.Save(ctx, project)
}

func (s *DesignService) createLayerSeparationResult(ctx context.Context, projectID string, target design.Node, req design.NodeActionRequest) (layerSeparationResult, error) {
	sourceData, sourceContentType, err := loadImageContent(ctx, target.Content)
	if err != nil {
		return layerSeparationResult{}, err
	}
	source, _, err := image.Decode(bytes.NewReader(sourceData))
	if err != nil {
		return layerSeparationResult{}, err
	}
	bounds := source.Bounds()
	canvasWidth := int64(bounds.Dx())
	canvasHeight := int64(bounds.Dy())
	canvas := image.NewRGBA(bounds)
	draw.Draw(canvas, bounds, source, bounds.Min, draw.Src)

	extraction, err := s.extractLayerSeparationText(ctx, target, req)
	if err != nil {
		return layerSeparationResult{}, err
	}
	for _, layer := range extraction.Layers {
		removeTextLayerFromImage(canvas, layer)
	}

	foregrounds := make([]layerSeparationForeground, 0, 1)
	if fullForeground, elementForegrounds, ok := s.createLayerSeparationForegroundCandidates(ctx, target, sourceData, sourceContentType, bounds, extraction); ok {
		if len(extraction.Layers) == 0 {
			if plainBackground, ok := plainLayerSeparationBackgroundImage(canvas, fullForeground.Mask, fullForeground.Rect); ok {
				if foreground, ok := s.persistLayerSeparationForeground(ctx, projectID, fullForeground); ok {
					foregrounds = append(foregrounds, foreground)
				}
				canvas = plainBackground
			}
		}
		if len(foregrounds) == 0 {
			for _, candidate := range elementForegrounds {
				foreground, ok := s.persistLayerSeparationForeground(ctx, projectID, candidate)
				if !ok {
					continue
				}
				removeForegroundMaskFromImage(canvas, foreground.Mask, foreground.Rect)
				foregrounds = append(foregrounds, foreground)
			}
		}
		if len(foregrounds) == 0 && len(extraction.Layers) == 0 {
			if foreground, ok := s.persistLayerSeparationForeground(ctx, projectID, fullForeground); ok {
				removeForegroundMaskFromImage(canvas, foreground.Mask, foreground.Rect)
				foregrounds = append(foregrounds, foreground)
			}
		}
		if len(extraction.Layers) == 0 && len(foregrounds) == 1 {
			if plainBackground, ok := plainLayerSeparationBackgroundImage(canvas, foregrounds[0].Mask, foregrounds[0].Rect); ok {
				canvas = plainBackground
			}
		}
	}

	backgroundID := newID()
	backgroundURL, backgroundSize, err := s.persistLayerSeparationImage(ctx, projectID, backgroundID, "background", canvas)
	if err != nil {
		return layerSeparationResult{}, err
	}

	textRenderData, err := layerSeparationTextRenderData(extraction, canvasWidth, canvasHeight)
	if err != nil {
		return layerSeparationResult{}, err
	}

	artifacts := make([]design.GeneratorTaskArtifact, 0, len(foregrounds)+2)
	for _, foreground := range foregrounds {
		artifacts = append(artifacts, design.GeneratorTaskArtifact{
			Type:    "image",
			Content: foreground.URL,
			Metadata: design.GeneratorTaskArtifactMetadata{
				ArtifactID:    foreground.ID,
				BBox:          append([]int64(nil), foreground.BBox...),
				Format:        generatorArtifactFormat("", foreground.URL),
				GeneratorName: layerSeparationGeneratorName,
				Height:        foreground.Height,
				Label:         layerSeparationForegroundLabel,
				NodeID:        foreground.ID,
				NodeName:      "Foreground Layer",
				SizeBytes:     0,
				Width:         foreground.Width,
			},
		})
	}
	artifacts = append(artifacts, design.GeneratorTaskArtifact{
		Type:    "image",
		Content: backgroundURL,
		Metadata: design.GeneratorTaskArtifactMetadata{
			ArtifactID:    backgroundID,
			Format:        generatorArtifactFormat("", backgroundURL),
			GeneratorName: layerSeparationGeneratorName,
			Height:        canvasHeight,
			Label:         layerSeparationBackgroundLabel,
			NodeID:        backgroundID,
			NodeName:      "Image",
			SizeBytes:     backgroundSize,
			Width:         canvasWidth,
		},
	}, design.GeneratorTaskArtifact{
		Type:    "text",
		Content: textRenderData,
		Metadata: design.GeneratorTaskArtifactMetadata{
			ArtifactID:    newID(),
			GeneratorName: layerSeparationGeneratorName,
			Height:        canvasHeight,
			Label:         layerSeparationTextLabel,
			Width:         canvasWidth,
		},
	})

	return layerSeparationResult{
		CanvasWidth:    canvasWidth,
		CanvasHeight:   canvasHeight,
		BackgroundID:   backgroundID,
		BackgroundURL:  backgroundURL,
		Foregrounds:    foregrounds,
		TextExtraction: extraction,
		Artifacts:      artifacts,
	}, nil
}

func (s *DesignService) extractLayerSeparationText(ctx context.Context, target design.Node, req design.NodeActionRequest) (design.TextExtraction, error) {
	if extraction, ok, err := textExtractionFromOptions(req.Options); ok || err != nil {
		return extraction, err
	}
	if s.textExtractor == nil {
		return design.TextExtraction{}, nil
	}
	return s.extractTextExtraction(ctx, target, req)
}

func (s *DesignService) createLayerSeparationForegroundCandidates(ctx context.Context, target design.Node, sourceData []byte, sourceContentType string, bounds image.Rectangle, extraction design.TextExtraction) (layerSeparationForegroundCandidate, []layerSeparationForegroundCandidate, bool) {
	if s.backgroundRemover == nil {
		return layerSeparationForegroundCandidate{}, nil, false
	}
	removed, err := s.backgroundRemover.RemoveBackground(ctx, design.BackgroundRemovalRequest{
		Image:       sourceData,
		ContentType: sourceContentType,
		Width:       bounds.Dx(),
		Height:      bounds.Dy(),
	})
	if err != nil || len(removed.Image) == 0 {
		return layerSeparationForegroundCandidate{}, nil, false
	}
	foregroundImage, _, err := image.Decode(bytes.NewReader(removed.Image))
	if err != nil {
		return layerSeparationForegroundCandidate{}, nil, false
	}
	foreground := image.NewNRGBA(foregroundImage.Bounds())
	draw.Draw(foreground, foreground.Bounds(), foregroundImage, foregroundImage.Bounds().Min, draw.Src)
	eraseTextLayersFromForeground(foreground, extraction)
	foregroundBounds := foreground.Bounds()
	rect, ok := alphaContentBounds(foreground, foregroundBounds, 12)
	if !ok {
		return layerSeparationForegroundCandidate{}, nil, false
	}
	mask, count := alphaMask(foreground, foregroundBounds, 12)
	if count == 0 {
		return layerSeparationForegroundCandidate{}, nil, false
	}
	full := newLayerSeparationForegroundCandidate(foreground, mask, rect, foregroundBounds)
	return full, layerSeparationElementCandidates(foreground, foregroundBounds), true
}

func (s *DesignService) persistLayerSeparationForeground(ctx context.Context, projectID string, candidate layerSeparationForegroundCandidate) (layerSeparationForeground, bool) {
	if candidate.Image == nil || candidate.Mask == nil || candidate.Rect.Empty() || len(candidate.BBox) < 4 {
		return layerSeparationForeground{}, false
	}
	foregroundID := newID()
	foregroundURL, _, err := s.persistLayerSeparationImage(ctx, projectID, foregroundID, "foreground", candidate.Image)
	if err != nil {
		return layerSeparationForeground{}, false
	}
	return layerSeparationForeground{
		ID:     foregroundID,
		URL:    foregroundURL,
		BBox:   append([]int64(nil), candidate.BBox...),
		Width:  candidate.Width,
		Height: candidate.Height,
		Mask:   candidate.Mask,
		Rect:   candidate.Rect,
	}, true
}

func newLayerSeparationForegroundCandidate(foreground *image.NRGBA, mask *image.Alpha, rect image.Rectangle, bounds image.Rectangle) layerSeparationForegroundCandidate {
	return layerSeparationForegroundCandidate{
		BBox: []int64{
			int64(rect.Min.X - bounds.Min.X),
			int64(rect.Min.Y - bounds.Min.Y),
			int64(rect.Max.X - bounds.Min.X),
			int64(rect.Max.Y - bounds.Min.Y),
		},
		Width:  int64(rect.Dx()),
		Height: int64(rect.Dy()),
		Mask:   mask,
		Rect:   rect,
		Image:  foregroundImageFromMask(foreground, mask, rect),
	}
}

func eraseTextLayersFromForeground(foreground *image.NRGBA, extraction design.TextExtraction) {
	if foreground == nil || len(extraction.Layers) == 0 {
		return
	}
	bounds := foreground.Bounds()
	if bounds.Dx()*bounds.Dy() < 4096 {
		return
	}
	for _, layer := range extraction.Layers {
		rect := normalizedTextMaskRect(bounds, layer)
		if rect.Empty() {
			continue
		}
		padding := clampInt(int(math.Round(math.Min(float64(rect.Dx()), float64(rect.Dy()))*0.14)), 2, 18)
		rect = image.Rect(rect.Min.X-padding, rect.Min.Y-padding, rect.Max.X+padding, rect.Max.Y+padding).Intersect(bounds)
		for y := rect.Min.Y; y < rect.Max.Y; y++ {
			for x := rect.Min.X; x < rect.Max.X; x++ {
				offset := foreground.PixOffset(x, y)
				foreground.Pix[offset+3] = 0
			}
		}
	}
}

func layerSeparationElementCandidates(foreground *image.NRGBA, bounds image.Rectangle) []layerSeparationForegroundCandidate {
	if foreground == nil || bounds.Empty() {
		return nil
	}
	width := bounds.Dx()
	height := bounds.Dy()
	visited := make([]bool, width*height)
	components := make([]layerSeparationForegroundCandidate, 0, 4)
	indexOf := func(x int, y int) int {
		return (y-bounds.Min.Y)*width + (x - bounds.Min.X)
	}
	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
		for x := bounds.Min.X; x < bounds.Max.X; x++ {
			index := indexOf(x, y)
			if visited[index] || foreground.NRGBAAt(x, y).A <= 12 {
				visited[index] = true
				continue
			}
			mask, rect, count := layerSeparationComponentMask(foreground, bounds, visited, x, y, indexOf)
			if !keepLayerSeparationElement(rect, count, bounds) {
				continue
			}
			components = append(components, newLayerSeparationForegroundCandidate(foreground, mask, rect, bounds))
		}
	}
	sort.Slice(components, func(i int, j int) bool {
		leftArea := components[i].Rect.Dx() * components[i].Rect.Dy()
		rightArea := components[j].Rect.Dx() * components[j].Rect.Dy()
		return leftArea > rightArea
	})
	if len(components) > 12 {
		components = components[:12]
	}
	return components
}

func layerSeparationComponentMask(foreground *image.NRGBA, bounds image.Rectangle, visited []bool, startX int, startY int, indexOf func(int, int) int) (*image.Alpha, image.Rectangle, int) {
	mask := image.NewAlpha(bounds)
	stack := []image.Point{{X: startX, Y: startY}}
	minX, minY := startX, startY
	maxX, maxY := startX+1, startY+1
	count := 0
	for len(stack) > 0 {
		point := stack[len(stack)-1]
		stack = stack[:len(stack)-1]
		if point.X < bounds.Min.X || point.X >= bounds.Max.X || point.Y < bounds.Min.Y || point.Y >= bounds.Max.Y {
			continue
		}
		index := indexOf(point.X, point.Y)
		if visited[index] {
			continue
		}
		visited[index] = true
		if foreground.NRGBAAt(point.X, point.Y).A <= 12 {
			continue
		}
		mask.SetAlpha(point.X, point.Y, color.Alpha{A: 255})
		count++
		if point.X < minX {
			minX = point.X
		}
		if point.Y < minY {
			minY = point.Y
		}
		if point.X+1 > maxX {
			maxX = point.X + 1
		}
		if point.Y+1 > maxY {
			maxY = point.Y + 1
		}
		stack = append(stack,
			image.Point{X: point.X + 1, Y: point.Y},
			image.Point{X: point.X - 1, Y: point.Y},
			image.Point{X: point.X, Y: point.Y + 1},
			image.Point{X: point.X, Y: point.Y - 1},
		)
	}
	return mask, image.Rect(minX, minY, maxX, maxY), count
}

func keepLayerSeparationElement(rect image.Rectangle, count int, bounds image.Rectangle) bool {
	if rect.Empty() || count <= 0 {
		return false
	}
	totalArea := bounds.Dx() * bounds.Dy()
	if totalArea <= 0 {
		return false
	}
	if totalArea < 4096 {
		return true
	}
	bboxArea := rect.Dx() * rect.Dy()
	minArea := maxInt(96, totalArea/6000)
	if count < minArea || bboxArea < minArea {
		return false
	}
	if float64(bboxArea)/float64(totalArea) > 0.18 {
		return false
	}
	if float64(rect.Dx())/float64(bounds.Dx()) > 0.62 || float64(rect.Dy())/float64(bounds.Dy()) > 0.62 {
		return false
	}
	return true
}

func foregroundImageFromMask(foreground *image.NRGBA, mask *image.Alpha, rect image.Rectangle) image.Image {
	cropped := image.NewNRGBA(image.Rect(0, 0, rect.Dx(), rect.Dy()))
	for y := rect.Min.Y; y < rect.Max.Y; y++ {
		for x := rect.Min.X; x < rect.Max.X; x++ {
			if mask.AlphaAt(x, y).A == 0 {
				continue
			}
			cropped.SetNRGBA(x-rect.Min.X, y-rect.Min.Y, foreground.NRGBAAt(x, y))
		}
	}
	return cropped
}

func (s *DesignService) persistLayerSeparationImage(ctx context.Context, projectID string, nodeID string, suffix string, img image.Image) (string, int64, error) {
	var output bytes.Buffer
	if err := png.Encode(&output, img); err != nil {
		return "", 0, err
	}
	if s.assets == nil {
		data := output.Bytes()
		return "data:image/png;base64," + base64.StdEncoding.EncodeToString(data), int64(len(data)), nil
	}
	data, contentType, err := encodeRasterAssetAsWebP(output.Bytes(), "image/png")
	if err != nil {
		return "", 0, err
	}
	object, err := s.assets.PutObject(ctx, design.AssetObjectRequest{
		FileName:    fmt.Sprintf("%s-%s-%s.png", projectID, nodeID, suffix),
		ContentType: contentType,
		Data:        data,
	})
	if err != nil {
		return "", 0, err
	}
	if strings.TrimSpace(object.PublicURL) == "" {
		return "", 0, fmt.Errorf("layer separation upload returned empty public URL")
	}
	return object.PublicURL, int64(len(data)), nil
}

func newLayerSeparationBackgroundNode(frame design.Node, result layerSeparationResult) design.Node {
	return design.Node{
		ID:        result.BackgroundID,
		Type:      design.NodeTypeImage,
		Title:     "Image",
		X:         frame.X,
		Y:         frame.Y,
		Width:     frame.Width,
		Height:    frame.Height,
		Content:   result.BackgroundURL,
		Tone:      "visual",
		Status:    "success",
		LayerRole: "clean-image",
	}
}

func newForegroundImageLayers(target design.Node, foregrounds []layerSeparationForeground, canvasWidth int64, canvasHeight int64) []design.Node {
	if len(foregrounds) == 0 || canvasWidth <= 0 || canvasHeight <= 0 {
		return nil
	}
	nodes := make([]design.Node, 0, len(foregrounds))
	for index, foreground := range foregrounds {
		if len(foreground.BBox) < 4 || strings.TrimSpace(foreground.URL) == "" {
			continue
		}
		x1 := clampFloat(float64(foreground.BBox[0])/float64(canvasWidth), 0, 1)
		y1 := clampFloat(float64(foreground.BBox[1])/float64(canvasHeight), 0, 1)
		x2 := clampFloat(float64(foreground.BBox[2])/float64(canvasWidth), x1, 1)
		y2 := clampFloat(float64(foreground.BBox[3])/float64(canvasHeight), y1, 1)
		width := target.Width * (x2 - x1)
		height := target.Height * (y2 - y1)
		if width <= 1 || height <= 1 {
			continue
		}
		nodes = append(nodes, design.Node{
			ID:        foreground.ID,
			Type:      design.NodeTypeImage,
			Title:     fmt.Sprintf("Foreground Layer %d", index+1),
			X:         target.X + target.Width*x1,
			Y:         target.Y + target.Height*y1,
			Width:     width,
			Height:    height,
			Content:   foreground.URL,
			Tone:      "separated-element",
			Status:    "success",
			ParentID:  target.ID,
			LayerRole: "foreground-image",
		})
	}
	return nodes
}

func layerSeparationArtifactsMessage(threadID string, artifacts []design.GeneratorTaskArtifact, createdAt time.Time) design.Message {
	content, _ := json.Marshal(toLayerSeparationArtifactWire(artifacts))
	return design.Message{
		ID:         newID(),
		Role:       "tool",
		Type:       "tool_use",
		Title:      layerSeparationMessageName,
		Content:    string(content),
		ThreadID:   threadID,
		ActionID:   threadID,
		StepID:     newID(),
		ToolCallID: "call_" + strings.ReplaceAll(newID(), "-", ""),
		Name:       layerSeparationMessageName,
		ToolHint:   layerSeparationMessageName,
		Status:     "success",
		CreatedAt:  createdAt,
	}
}

func toLayerSeparationArtifactWire(artifacts []design.GeneratorTaskArtifact) []map[string]any {
	items := make([]map[string]any, 0, len(artifacts))
	for _, artifact := range artifacts {
		items = append(items, map[string]any{
			"type":    artifact.Type,
			"content": artifact.Content,
			"metadata": map[string]any{
				"artifact_id":    artifact.Metadata.ArtifactID,
				"bbox":           artifact.Metadata.BBox,
				"format":         artifact.Metadata.Format,
				"generator_name": artifact.Metadata.GeneratorName,
				"height":         artifact.Metadata.Height,
				"label":          artifact.Metadata.Label,
				"node_id":        artifact.Metadata.NodeID,
				"node_name":      artifact.Metadata.NodeName,
				"size_bytes":     artifact.Metadata.SizeBytes,
				"width":          artifact.Metadata.Width,
			},
		})
	}
	return items
}

func removeForegroundMaskFromImage(img *image.RGBA, mask *image.Alpha, rect image.Rectangle) {
	if mask == nil || rect.Empty() {
		return
	}
	bounds := img.Bounds()
	rect = rect.Intersect(bounds)
	if rect.Empty() {
		return
	}
	radius := clampInt(int(math.Round(math.Min(float64(rect.Dx()), float64(rect.Dy()))*0.025)), 2, 10)
	mask, count := dilateTextMask(mask, rect, radius)
	if count == 0 {
		return
	}
	source := image.NewRGBA(bounds)
	draw.Draw(source, bounds, img, bounds.Min, draw.Src)
	for y := rect.Min.Y; y < rect.Max.Y; y++ {
		for x := rect.Min.X; x < rect.Max.X; x++ {
			if mask.AlphaAt(x, y).A == 0 {
				continue
			}
			img.SetRGBA(x, y, estimatedRectBackgroundColor(source, rect, x, y))
		}
	}
	softenMaskedPixels(img, mask, rect)
}

func plainLayerSeparationBackgroundImage(img *image.RGBA, mask *image.Alpha, rect image.Rectangle) (*image.RGBA, bool) {
	if img == nil || mask == nil || rect.Empty() {
		return nil, false
	}
	bounds := img.Bounds()
	if bounds.Empty() {
		return nil, false
	}
	radius := clampInt(int(math.Round(math.Min(float64(rect.Dx()), float64(rect.Dy()))*0.02)), 3, 18)
	expandedMask, _ := dilateTextMask(mask, bounds, radius)
	stats, ok := unmaskedColorStats(img, expandedMask, bounds)
	if !ok || stats.StdDev > 24 {
		return nil, false
	}
	bg := image.NewRGBA(bounds)
	fill := colorRGBA(int(math.Round(stats.R)), int(math.Round(stats.G)), int(math.Round(stats.B)), int(math.Round(stats.A)))
	draw.Draw(bg, bounds, &image.Uniform{C: fill}, image.Point{}, draw.Src)
	return bg, true
}

type layerSeparationColorStats struct {
	Count  int64
	R      float64
	G      float64
	B      float64
	A      float64
	StdDev float64
}

func unmaskedColorStats(img *image.RGBA, mask *image.Alpha, bounds image.Rectangle) (layerSeparationColorStats, bool) {
	stride := clampInt(int(math.Ceil(float64(maxInt(bounds.Dx(), bounds.Dy()))/640)), 1, 12)
	var count int64
	var r, g, b, a float64
	var rr, gg, bb float64
	for y := bounds.Min.Y; y < bounds.Max.Y; y += stride {
		for x := bounds.Min.X; x < bounds.Max.X; x += stride {
			if mask.AlphaAt(x, y).A != 0 {
				continue
			}
			c := img.RGBAAt(x, y)
			cfR := float64(c.R)
			cfG := float64(c.G)
			cfB := float64(c.B)
			cfA := float64(c.A)
			r += cfR
			g += cfG
			b += cfB
			a += cfA
			rr += cfR * cfR
			gg += cfG * cfG
			bb += cfB * cfB
			count++
		}
	}
	if count < 32 {
		return layerSeparationColorStats{}, false
	}
	divisor := float64(count)
	meanR := r / divisor
	meanG := g / divisor
	meanB := b / divisor
	varR := math.Max(0, rr/divisor-meanR*meanR)
	varG := math.Max(0, gg/divisor-meanG*meanG)
	varB := math.Max(0, bb/divisor-meanB*meanB)
	return layerSeparationColorStats{
		Count:  count,
		R:      meanR,
		G:      meanG,
		B:      meanB,
		A:      a / divisor,
		StdDev: math.Sqrt((varR + varG + varB) / 3),
	}, true
}

func alphaContentBounds(img image.Image, bounds image.Rectangle, threshold uint8) (image.Rectangle, bool) {
	minX, minY := bounds.Max.X, bounds.Max.Y
	maxX, maxY := bounds.Min.X, bounds.Min.Y
	found := false
	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
		for x := bounds.Min.X; x < bounds.Max.X; x++ {
			if alphaAt(img, x, y) <= threshold {
				continue
			}
			if x < minX {
				minX = x
			}
			if y < minY {
				minY = y
			}
			if x+1 > maxX {
				maxX = x + 1
			}
			if y+1 > maxY {
				maxY = y + 1
			}
			found = true
		}
	}
	if !found {
		return image.Rectangle{}, false
	}
	return image.Rect(minX, minY, maxX, maxY), true
}

func alphaMask(img image.Image, bounds image.Rectangle, threshold uint8) (*image.Alpha, int) {
	mask := image.NewAlpha(bounds)
	count := 0
	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
		for x := bounds.Min.X; x < bounds.Max.X; x++ {
			if alphaAt(img, x, y) <= threshold {
				continue
			}
			mask.SetAlpha(x, y, color.Alpha{A: 255})
			count++
		}
	}
	return mask, count
}

func alphaAt(img image.Image, x int, y int) uint8 {
	_, _, _, a := img.At(x, y).RGBA()
	return uint8(a >> 8)
}

func cropImage(img image.Image, rect image.Rectangle) image.Image {
	cropped := image.NewNRGBA(image.Rect(0, 0, rect.Dx(), rect.Dy()))
	draw.Draw(cropped, cropped.Bounds(), img, rect.Min, draw.Src)
	return cropped
}

type layerSeparationTextDocument struct {
	Layers     []layerSeparationTextLayer `json:"layers"`
	CanvasSize layerSeparationCanvasSize  `json:"canvas_size"`
}

type layerSeparationCanvasSize struct {
	Width  int64 `json:"width"`
	Height int64 `json:"height"`
}

type layerSeparationTextLayer struct {
	TextInfo layerSeparationTextInfo `json:"text_info"`
	X        float64                 `json:"x"`
	Y        float64                 `json:"y"`
	W        float64                 `json:"w"`
	H        float64                 `json:"h"`
}

type layerSeparationTextInfo struct {
	Text        string  `json:"text"`
	FontSizePx  int64   `json:"font_size_px"`
	FontFamily  string  `json:"font_family"`
	FontWeight  any     `json:"font_weight"`
	FontStyle   string  `json:"font_style"`
	ColorCSS    string  `json:"color_css"`
	TextAlign   string  `json:"text_align"`
	Leading     float64 `json:"leading"`
	Tracking    float64 `json:"tracking"`
	Rotation    float64 `json:"rotation"`
	LeadingTrim string  `json:"leading_trim"`
}

func layerSeparationTextRenderData(extraction design.TextExtraction, canvasWidth int64, canvasHeight int64) (string, error) {
	doc := layerSeparationTextDocument{
		Layers: make([]layerSeparationTextLayer, 0, len(extraction.Layers)),
		CanvasSize: layerSeparationCanvasSize{
			Width:  canvasWidth,
			Height: canvasHeight,
		},
	}
	for _, layer := range extraction.Layers {
		text := strings.TrimSpace(layer.Text)
		if text == "" {
			continue
		}
		x := clamp01(layer.X)
		y := clamp01(layer.Y)
		width := clamp01(layer.Width)
		height := clamp01(layer.Height)
		if x+width > 1 {
			width = 1 - x
		}
		if y+height > 1 {
			height = 1 - y
		}
		if width <= 0 || height <= 0 {
			continue
		}
		fontSize := layer.FontSize
		if fontSize <= 0 {
			fontSize = math.Max(10, float64(canvasHeight)*height*0.72)
		}
		lineHeight := layer.LineHeight
		if lineHeight <= 0 {
			lineHeight = 1.2
		}
		fontFamily := strings.TrimSpace(layer.FontFamily)
		if fontFamily == "" {
			fontFamily = "Inter"
		}
		doc.Layers = append(doc.Layers, layerSeparationTextLayer{
			TextInfo: layerSeparationTextInfo{
				Text:        text,
				FontSizePx:  int64(math.Round(fontSize)),
				FontFamily:  fontFamily,
				FontWeight:  layerSeparationFontWeight(layer.FontWeight),
				FontStyle:   layerSeparationFontStyle(layer.FontWeight),
				ColorCSS:    layerSeparationColorCSS(layer.Color),
				TextAlign:   layerSeparationTextAlign(layer.TextAlign),
				Leading:     lineHeight,
				Tracking:    layer.LetterSpacing,
				Rotation:    layer.Rotation,
				LeadingTrim: "CAP_HEIGHT",
			},
			X: x * float64(canvasWidth),
			Y: y * float64(canvasHeight),
			W: width * float64(canvasWidth),
			H: height * float64(canvasHeight),
		})
	}
	data, err := json.Marshal(doc)
	if err != nil {
		return "", err
	}
	return string(data), nil
}

func layerSeparationFontWeight(value string) any {
	value = strings.TrimSpace(value)
	if value == "" {
		return 400
	}
	if weight, err := strconv.Atoi(value); err == nil {
		return weight
	}
	return value
}

func layerSeparationFontStyle(value string) string {
	if strings.Contains(strings.ToLower(strings.TrimSpace(value)), "italic") {
		return "italic"
	}
	return "normal"
}

func layerSeparationTextAlign(value string) string {
	switch strings.ToLower(strings.TrimSpace(value)) {
	case "left":
		return "start"
	case "right":
		return "end"
	case "center":
		return "center"
	default:
		return "start"
	}
}

func layerSeparationColorCSS(value string) string {
	parsed, ok := parseCanvasColor(value)
	if !ok {
		return "rgba(25, 25, 25, 1.0)"
	}
	alpha := float64(parsed.A) / 255
	return fmt.Sprintf("rgba(%d, %d, %d, %.3g)", parsed.R, parsed.G, parsed.B, alpha)
}