feat: admin image generation via Cloudflare Workers AI

- Add cfai/image.go: ImageGenClient with GenerateImage, GenerateImageFromReference, AllImageModels (9 models) - Add handlers_image.go: GET /api/admin/image-gen/models + POST /api/admin/image-gen (JSON + multipart) - Wire ImageGen client in main.go + server.go Dependencies - Add admin/image-gen SvelteKit page: type toggle, model selector, prompt, reference img2img, advanced options, result panel, history, save-as-cover, download - Add SvelteKit proxy route api/admin/image-gen forwarding to Go backend - Add admin_nav_image_gen message key to all 5 locale files - Add Image Gen nav link to admin layout
2026-04-04 11:46:22 +05:00
parent aaa008ac99
commit d1b7d3e36c
13 changed files with 1320 additions and 1 deletions
--- a/backend/cmd/backend/main.go
+++ b/backend/cmd/backend/main.go
@@ -124,6 +124,15 @@ func run() error {
 		log.Info("CFAI_ACCOUNT_ID/CFAI_API_TOKEN not set — CF AI voices unavailable in backend")
 	}

+	// ── Cloudflare Workers AI Image Generation ────────────────────────────────
+	var imageGenClient cfai.ImageGenClient
+	if cfg.CFAI.AccountID != "" && cfg.CFAI.APIToken != "" {
+		imageGenClient = cfai.NewImageGen(cfg.CFAI.AccountID, cfg.CFAI.APIToken)
+		log.Info("cloudflare AI image generation enabled")
+	} else {
+		log.Info("CFAI_ACCOUNT_ID/CFAI_API_TOKEN not set — image generation unavailable")
+	}
+
 	// ── Meilisearch (search reads only; indexing is the runner's job) ────────
 	var searchIndex meili.Client
 	if cfg.Meilisearch.URL != "" {
@@ -174,6 +183,7 @@ func run() error {
 			Kokoro:           kokoroClient,
 			PocketTTS:        pocketTTSClient,
 			CFAI:             cfaiClient,
+			ImageGen:         imageGenClient,
 			Log:              log,
 		},
 	)
--- a/backend/internal/backend/handlers_image.go
+++ b/backend/internal/backend/handlers_image.go
@@ -0,0 +1,234 @@
+package backend
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+
+	"github.com/libnovel/backend/internal/cfai"
+)
+
+// handleAdminImageGenModels handles GET /api/admin/image-gen/models.
+// Returns the list of supported Cloudflare AI image generation models.
+func (s *Server) handleAdminImageGenModels(w http.ResponseWriter, r *http.Request) {
+	if s.deps.ImageGen == nil {
+		jsonError(w, http.StatusServiceUnavailable, "image generation not configured (CFAI_ACCOUNT_ID/CFAI_API_TOKEN missing)")
+		return
+	}
+	models := s.deps.ImageGen.Models()
+	writeJSON(w, 0, map[string]any{"models": models})
+}
+
+// imageGenRequest is the JSON body for POST /api/admin/image-gen.
+type imageGenRequest struct {
+	// Prompt is the text description of the desired image.
+	Prompt string `json:"prompt"`
+
+	// Model is the CF Workers AI model ID (e.g. "@cf/black-forest-labs/flux-2-dev").
+	// Defaults to the recommended model for the given type.
+	Model string `json:"model"`
+
+	// Type is either "cover" or "chapter".
+	Type string `json:"type"`
+
+	// Slug is the book slug. Required for cover; required for chapter.
+	Slug string `json:"slug"`
+
+	// Chapter number (1-based). Required when type == "chapter".
+	Chapter int `json:"chapter"`
+
+	// ReferenceImageB64 is an optional base64-encoded PNG/JPEG reference image.
+	// When present the img2img path is used.
+	ReferenceImageB64 string `json:"reference_image_b64"`
+
+	// NumSteps overrides inference steps (default 20).
+	NumSteps int `json:"num_steps"`
+
+	// Width / Height override output dimensions (0 = model default).
+	Width  int `json:"width"`
+	Height int `json:"height"`
+
+	// Guidance overrides prompt guidance scale (0 = model default).
+	Guidance float64 `json:"guidance"`
+
+	// Strength for img2img: 0.0–1.0, default 0.75.
+	Strength float64 `json:"strength"`
+
+	// SaveToCover when true stores the result as the book cover in MinIO
+	// (overwriting any existing cover) and sets the book's cover URL.
+	// Only valid when type == "cover".
+	SaveToCover bool `json:"save_to_cover"`
+}
+
+// imageGenResponse is the JSON body returned by POST /api/admin/image-gen.
+type imageGenResponse struct {
+	// ImageB64 is the generated image as a base64-encoded PNG string.
+	ImageB64 string `json:"image_b64"`
+	// ContentType is "image/png" or "image/jpeg".
+	ContentType string `json:"content_type"`
+	// Saved indicates whether the image was persisted to MinIO.
+	Saved bool `json:"saved"`
+	// CoverURL is the URL the cover is now served from (only set when Saved==true).
+	CoverURL string `json:"cover_url,omitempty"`
+	// Model is the model that was used.
+	Model string `json:"model"`
+	// Bytes is the raw image size in bytes.
+	Bytes int `json:"bytes"`
+}
+
+// handleAdminImageGen handles POST /api/admin/image-gen.
+//
+// Generates an image using Cloudflare Workers AI and optionally stores it.
+// Multipart/form-data is also accepted so the reference image can be uploaded
+// directly; otherwise the reference is expected as base64 JSON.
+func (s *Server) handleAdminImageGen(w http.ResponseWriter, r *http.Request) {
+	if s.deps.ImageGen == nil {
+		jsonError(w, http.StatusServiceUnavailable, "image generation not configured (CFAI_ACCOUNT_ID/CFAI_API_TOKEN missing)")
+		return
+	}
+
+	var req imageGenRequest
+	var refImageData []byte
+
+	ct := r.Header.Get("Content-Type")
+	if strings.HasPrefix(ct, "multipart/form-data") {
+		// Multipart: parse JSON fields from a "json" part + optional "reference" file part.
+		if err := r.ParseMultipartForm(32 << 20); err != nil {
+			jsonError(w, http.StatusBadRequest, "parse multipart: "+err.Error())
+			return
+		}
+		if jsonPart := r.FormValue("json"); jsonPart != "" {
+			if err := json.Unmarshal([]byte(jsonPart), &req); err != nil {
+				jsonError(w, http.StatusBadRequest, "parse json field: "+err.Error())
+				return
+			}
+		}
+		if f, _, err := r.FormFile("reference"); err == nil {
+			defer f.Close()
+			refImageData, _ = io.ReadAll(f)
+		}
+	} else {
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			jsonError(w, http.StatusBadRequest, "parse body: "+err.Error())
+			return
+		}
+		if req.ReferenceImageB64 != "" {
+			var decErr error
+			refImageData, decErr = base64.StdEncoding.DecodeString(req.ReferenceImageB64)
+			if decErr != nil {
+				// Try std without padding
+				refImageData, decErr = base64.RawStdEncoding.DecodeString(req.ReferenceImageB64)
+				if decErr != nil {
+					jsonError(w, http.StatusBadRequest, "decode reference_image_b64: "+decErr.Error())
+					return
+				}
+			}
+		}
+	}
+
+	if strings.TrimSpace(req.Prompt) == "" {
+		jsonError(w, http.StatusBadRequest, "prompt is required")
+		return
+	}
+	if req.Type != "cover" && req.Type != "chapter" {
+		jsonError(w, http.StatusBadRequest, `type must be "cover" or "chapter"`)
+		return
+	}
+	if req.Slug == "" {
+		jsonError(w, http.StatusBadRequest, "slug is required")
+		return
+	}
+	if req.Type == "chapter" && req.Chapter <= 0 {
+		jsonError(w, http.StatusBadRequest, "chapter must be > 0 when type is chapter")
+		return
+	}
+
+	// Resolve model
+	model := cfai.ImageModel(req.Model)
+	if model == "" {
+		if req.Type == "cover" {
+			model = cfai.DefaultImageModel
+		} else {
+			model = cfai.ImageModelFlux2Klein4B
+		}
+	}
+
+	imgReq := cfai.ImageRequest{
+		Prompt:   req.Prompt,
+		Model:    model,
+		NumSteps: req.NumSteps,
+		Width:    req.Width,
+		Height:   req.Height,
+		Guidance: req.Guidance,
+		Strength: req.Strength,
+	}
+
+	s.deps.Log.Info("admin: image gen requested",
+		"type", req.Type, "slug", req.Slug, "chapter", req.Chapter,
+		"model", model, "has_reference", len(refImageData) > 0)
+
+	var imgData []byte
+	var genErr error
+	if len(refImageData) > 0 {
+		imgData, genErr = s.deps.ImageGen.GenerateImageFromReference(r.Context(), imgReq, refImageData)
+	} else {
+		imgData, genErr = s.deps.ImageGen.GenerateImage(r.Context(), imgReq)
+	}
+	if genErr != nil {
+		s.deps.Log.Error("admin: image gen failed", "err", genErr)
+		jsonError(w, http.StatusBadGateway, "image generation failed: "+genErr.Error())
+		return
+	}
+
+	contentType := sniffImageContentType(imgData)
+
+	// ── Optional persistence ──────────────────────────────────────────────────
+	var saved bool
+	var coverURL string
+
+	if req.SaveToCover && req.Type == "cover" && s.deps.CoverStore != nil {
+		if err := s.deps.CoverStore.PutCover(r.Context(), req.Slug, imgData, contentType); err != nil {
+			s.deps.Log.Error("admin: save generated cover failed", "slug", req.Slug, "err", err)
+			// Non-fatal: still return the image
+		} else {
+			saved = true
+			coverURL = fmt.Sprintf("/api/cover/local/%s", req.Slug)
+			s.deps.Log.Info("admin: generated cover saved", "slug", req.Slug, "bytes", len(imgData))
+		}
+	}
+
+	// Encode result as base64
+	b64 := base64.StdEncoding.EncodeToString(imgData)
+
+	writeJSON(w, 0, imageGenResponse{
+		ImageB64:    b64,
+		ContentType: contentType,
+		Saved:       saved,
+		CoverURL:    coverURL,
+		Model:       string(model),
+		Bytes:       len(imgData),
+	})
+}
+
+// sniffImageContentType returns the MIME type of the image bytes.
+func sniffImageContentType(data []byte) string {
+	if len(data) >= 4 {
+		// PNG: 0x89 P N G
+		if data[0] == 0x89 && data[1] == 0x50 && data[2] == 0x4e && data[3] == 0x47 {
+			return "image/png"
+		}
+		// JPEG: FF D8 FF
+		if data[0] == 0xFF && data[1] == 0xD8 && data[2] == 0xFF {
+			return "image/jpeg"
+		}
+		// WebP: RIFF....WEBP
+		if len(data) >= 12 && data[0] == 'R' && data[1] == 'I' && data[2] == 'F' && data[3] == 'F' &&
+			data[8] == 'W' && data[9] == 'E' && data[10] == 'B' && data[11] == 'P' {
+			return "image/webp"
+		}
+	}
+	return "image/png"
+}
--- a/backend/internal/backend/server.go
+++ b/backend/internal/backend/server.go
@@ -73,6 +73,9 @@ type Dependencies struct {
 	// CFAI is the Cloudflare Workers AI TTS client (used for voice sample
 	// generation and audio-stream live TTS; audio task generation is done by the runner).
 	CFAI cfai.Client
+	// ImageGen is the Cloudflare Workers AI image generation client.
+	// If nil, image generation endpoints return 503.
+	ImageGen cfai.ImageGenClient
 	// Log is the structured logger.
 	Log *slog.Logger
 }
@@ -183,6 +186,10 @@ func (s *Server) ListenAndServe(ctx context.Context) error {
 	mux.HandleFunc("POST /api/admin/audio/bulk", s.handleAdminAudioBulk)
 	mux.HandleFunc("POST /api/admin/audio/cancel-bulk", s.handleAdminAudioCancelBulk)

+	// Admin image generation endpoints
+	mux.HandleFunc("GET /api/admin/image-gen/models", s.handleAdminImageGenModels)
+	mux.HandleFunc("POST /api/admin/image-gen", s.handleAdminImageGen)
+
 	// Voices list
 	mux.HandleFunc("GET /api/voices", s.handleVoices)

--- a/backend/internal/cfai/image.go
+++ b/backend/internal/cfai/image.go
@@ -0,0 +1,312 @@
+// Image generation via Cloudflare Workers AI text-to-image models.
+//
+// API reference:
+//
+//	POST https://api.cloudflare.com/client/v4/accounts/{accountID}/ai/run/{model}
+//	Authorization: Bearer {apiToken}
+//	Content-Type:  application/json
+//
+// Text-only request (all models):
+//
+//	{ "prompt": "...", "num_steps": 20 }
+//
+// Reference-image request:
+//   - FLUX models: { "prompt": "...", "image_b64": "<base64>" }
+//   - SD img2img:  { "prompt": "...", "image": [r,g,b,a,...], "strength": 0.75 }
+//
+// All models return raw PNG bytes on success (Content-Type: image/png).
+//
+// Recommended models for LibNovel:
+//   - Book covers (no reference): flux-2-dev, flux-2-klein-9b, lucid-origin
+//   - Chapter images (speed):     flux-2-klein-4b, flux-1-schnell
+//   - With reference image:       flux-2-dev, flux-2-klein-9b, sd-v1-5-img2img
+package cfai
+
+import (
+	"bytes"
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"image"
+	_ "image/jpeg" // register JPEG decoder
+	_ "image/png"  // register PNG decoder
+	"io"
+	"net/http"
+	"time"
+)
+
+// ImageModel identifies a Cloudflare Workers AI text-to-image model.
+type ImageModel string
+
+const (
+	// ImageModelFlux2Dev — best quality, multi-reference. Recommended for covers.
+	ImageModelFlux2Dev ImageModel = "@cf/black-forest-labs/flux-2-dev"
+	// ImageModelFlux2Klein9B — 9B params, multi-reference. Good for covers.
+	ImageModelFlux2Klein9B ImageModel = "@cf/black-forest-labs/flux-2-klein-9b"
+	// ImageModelFlux2Klein4B — ultra-fast, unified gen+edit. Recommended for chapters.
+	ImageModelFlux2Klein4B ImageModel = "@cf/black-forest-labs/flux-2-klein-4b"
+	// ImageModelFlux1Schnell — fastest, text-only. Good for quick illustrations.
+	ImageModelFlux1Schnell ImageModel = "@cf/black-forest-labs/flux-1-schnell"
+	// ImageModelSDXLLightning — fast 1024px generation.
+	ImageModelSDXLLightning ImageModel = "@cf/bytedance/stable-diffusion-xl-lightning"
+	// ImageModelSD15Img2Img — explicit img2img with flat RGBA reference.
+	ImageModelSD15Img2Img ImageModel = "@cf/runwayml/stable-diffusion-v1-5-img2img"
+	// ImageModelSDXLBase — Stability AI SDXL base.
+	ImageModelSDXLBase ImageModel = "@cf/stabilityai/stable-diffusion-xl-base-1.0"
+	// ImageModelLucidOrigin — Leonardo AI; strong prompt adherence.
+	ImageModelLucidOrigin ImageModel = "@cf/leonardo/lucid-origin"
+	// ImageModelPhoenix10 — Leonardo AI; accurate text rendering.
+	ImageModelPhoenix10 ImageModel = "@cf/leonardo/phoenix-1.0"
+
+	// DefaultImageModel is the default model for book-cover generation.
+	DefaultImageModel = ImageModelFlux2Dev
+)
+
+// ImageModelInfo describes a single image generation model.
+type ImageModelInfo struct {
+	ID             string   `json:"id"`
+	Label          string   `json:"label"`
+	Provider       string   `json:"provider"`
+	SupportsRef    bool     `json:"supports_ref"`
+	RecommendedFor []string `json:"recommended_for"` // "cover" and/or "chapter"
+	Description    string   `json:"description"`
+}
+
+// AllImageModels returns metadata about every supported image model.
+func AllImageModels() []ImageModelInfo {
+	return []ImageModelInfo{
+		{
+			ID: string(ImageModelFlux2Dev), Label: "FLUX.2 Dev", Provider: "Black Forest Labs",
+			SupportsRef: true, RecommendedFor: []string{"cover"},
+			Description: "Best quality; multi-reference editing. Recommended for book covers.",
+		},
+		{
+			ID: string(ImageModelFlux2Klein9B), Label: "FLUX.2 Klein 9B", Provider: "Black Forest Labs",
+			SupportsRef: true, RecommendedFor: []string{"cover"},
+			Description: "9B parameters with multi-reference support.",
+		},
+		{
+			ID: string(ImageModelFlux2Klein4B), Label: "FLUX.2 Klein 4B", Provider: "Black Forest Labs",
+			SupportsRef: true, RecommendedFor: []string{"chapter"},
+			Description: "Ultra-fast unified gen+edit. Recommended for chapter images.",
+		},
+		{
+			ID: string(ImageModelFlux1Schnell), Label: "FLUX.1 Schnell", Provider: "Black Forest Labs",
+			SupportsRef: false, RecommendedFor: []string{"chapter"},
+			Description: "Fastest inference. Good for quick chapter illustrations.",
+		},
+		{
+			ID: string(ImageModelSDXLLightning), Label: "SDXL Lightning", Provider: "ByteDance",
+			SupportsRef: false, RecommendedFor: []string{"chapter"},
+			Description: "Lightning-fast 1024px images in a few steps.",
+		},
+		{
+			ID: string(ImageModelSD15Img2Img), Label: "SD 1.5 img2img", Provider: "RunwayML",
+			SupportsRef: true, RecommendedFor: []string{"cover", "chapter"},
+			Description: "Explicit img2img: generates from a reference image + prompt.",
+		},
+		{
+			ID: string(ImageModelSDXLBase), Label: "SDXL Base 1.0", Provider: "Stability AI",
+			SupportsRef: false, RecommendedFor: []string{"cover"},
+			Description: "Stable Diffusion XL base model.",
+		},
+		{
+			ID: string(ImageModelLucidOrigin), Label: "Lucid Origin", Provider: "Leonardo AI",
+			SupportsRef: false, RecommendedFor: []string{"cover"},
+			Description: "Highly prompt-responsive; strong graphic design and HD renders.",
+		},
+		{
+			ID: string(ImageModelPhoenix10), Label: "Phoenix 1.0", Provider: "Leonardo AI",
+			SupportsRef: false, RecommendedFor: []string{"cover"},
+			Description: "Exceptional prompt adherence; accurate text rendering.",
+		},
+	}
+}
+
+// ImageRequest is the input to GenerateImage / GenerateImageFromReference.
+type ImageRequest struct {
+	// Prompt is the text description of the desired image.
+	Prompt string
+	// Model is the CF Workers AI model. Defaults to DefaultImageModel when empty.
+	Model ImageModel
+	// NumSteps controls inference quality (default 20). Range: 1–20.
+	NumSteps int
+	// Width and Height in pixels. 0 = model default (typically 1024x1024).
+	Width, Height int
+	// Guidance controls prompt adherence (default 7.5).
+	Guidance float64
+	// Strength for img2img: 0.0 = copy reference, 1.0 = ignore reference (default 0.75).
+	Strength float64
+}
+
+// ImageGenClient generates images via Cloudflare Workers AI.
+type ImageGenClient interface {
+	// GenerateImage creates an image from a text prompt only.
+	// Returns raw PNG bytes.
+	GenerateImage(ctx context.Context, req ImageRequest) ([]byte, error)
+
+	// GenerateImageFromReference creates an image from a text prompt + reference image.
+	// refImage should be PNG or JPEG bytes. Returns raw PNG bytes.
+	GenerateImageFromReference(ctx context.Context, req ImageRequest, refImage []byte) ([]byte, error)
+
+	// Models returns metadata about all supported image models.
+	Models() []ImageModelInfo
+}
+
+// imageGenHTTPClient is the concrete CF AI image generation client.
+type imageGenHTTPClient struct {
+	accountID string
+	apiToken  string
+	http      *http.Client
+}
+
+// NewImageGen returns an ImageGenClient for the given Cloudflare account.
+func NewImageGen(accountID, apiToken string) ImageGenClient {
+	return &imageGenHTTPClient{
+		accountID: accountID,
+		apiToken:  apiToken,
+		http:      &http.Client{Timeout: 5 * time.Minute},
+	}
+}
+
+// GenerateImage generates an image from text only.
+func (c *imageGenHTTPClient) GenerateImage(ctx context.Context, req ImageRequest) ([]byte, error) {
+	req = applyImageDefaults(req)
+	body := map[string]any{
+		"prompt":    req.Prompt,
+		"num_steps": req.NumSteps,
+	}
+	if req.Width > 0 {
+		body["width"] = req.Width
+	}
+	if req.Height > 0 {
+		body["height"] = req.Height
+	}
+	if req.Guidance > 0 {
+		body["guidance"] = req.Guidance
+	}
+	return c.callImageAPI(ctx, req.Model, body)
+}
+
+// GenerateImageFromReference generates an image from a text prompt + reference image.
+func (c *imageGenHTTPClient) GenerateImageFromReference(ctx context.Context, req ImageRequest, refImage []byte) ([]byte, error) {
+	if len(refImage) == 0 {
+		return c.GenerateImage(ctx, req)
+	}
+	req = applyImageDefaults(req)
+
+	var body map[string]any
+	if req.Model == ImageModelSD15Img2Img {
+		pixels, err := decodeImageToRGBA(refImage)
+		if err != nil {
+			return nil, fmt.Errorf("cfai/image: decode reference: %w", err)
+		}
+		strength := req.Strength
+		if strength <= 0 {
+			strength = 0.75
+		}
+		body = map[string]any{
+			"prompt":    req.Prompt,
+			"image":     pixels,
+			"strength":  strength,
+			"num_steps": req.NumSteps,
+		}
+	} else {
+		b64 := base64.StdEncoding.EncodeToString(refImage)
+		body = map[string]any{
+			"prompt":    req.Prompt,
+			"image_b64": b64,
+			"num_steps": req.NumSteps,
+		}
+		if req.Strength > 0 {
+			body["strength"] = req.Strength
+		}
+	}
+	if req.Width > 0 {
+		body["width"] = req.Width
+	}
+	if req.Height > 0 {
+		body["height"] = req.Height
+	}
+	if req.Guidance > 0 {
+		body["guidance"] = req.Guidance
+	}
+	return c.callImageAPI(ctx, req.Model, body)
+}
+
+// Models returns all supported image model metadata.
+func (c *imageGenHTTPClient) Models() []ImageModelInfo {
+	return AllImageModels()
+}
+
+func (c *imageGenHTTPClient) callImageAPI(ctx context.Context, model ImageModel, body map[string]any) ([]byte, error) {
+	encoded, err := json.Marshal(body)
+	if err != nil {
+		return nil, fmt.Errorf("cfai/image: marshal: %w", err)
+	}
+	url := fmt.Sprintf("https://api.cloudflare.com/client/v4/accounts/%s/ai/run/%s",
+		c.accountID, string(model))
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(encoded))
+	if err != nil {
+		return nil, fmt.Errorf("cfai/image: build request: %w", err)
+	}
+	req.Header.Set("Authorization", "Bearer "+c.apiToken)
+	req.Header.Set("Content-Type", "application/json")
+
+	resp, err := c.http.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("cfai/image: http: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		errBody, _ := io.ReadAll(resp.Body)
+		msg := string(errBody)
+		if len(msg) > 300 {
+			msg = msg[:300]
+		}
+		return nil, fmt.Errorf("cfai/image: model %s returned %d: %s", model, resp.StatusCode, msg)
+	}
+
+	data, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("cfai/image: read response: %w", err)
+	}
+	return data, nil
+}
+
+func applyImageDefaults(req ImageRequest) ImageRequest {
+	if req.Model == "" {
+		req.Model = DefaultImageModel
+	}
+	if req.NumSteps <= 0 {
+		req.NumSteps = 20
+	}
+	return req
+}
+
+// decodeImageToRGBA decodes PNG/JPEG bytes to a flat []uint8 RGBA pixel array
+// required by the stable-diffusion-v1-5-img2img model.
+func decodeImageToRGBA(data []byte) ([]uint8, error) {
+	img, _, err := image.Decode(bytes.NewReader(data))
+	if err != nil {
+		return nil, fmt.Errorf("decode image: %w", err)
+	}
+	bounds := img.Bounds()
+	w := bounds.Max.X - bounds.Min.X
+	h := bounds.Max.Y - bounds.Min.Y
+	pixels := make([]uint8, w*h*4)
+	idx := 0
+	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
+		for x := bounds.Min.X; x < bounds.Max.X; x++ {
+			r, g, b, a := img.At(x, y).RGBA()
+			pixels[idx] = uint8(r >> 8)
+			pixels[idx+1] = uint8(g >> 8)
+			pixels[idx+2] = uint8(b >> 8)
+			pixels[idx+3] = uint8(a >> 8)
+			idx += 4
+		}
+	}
+	return pixels, nil
+}