almost full rewrite of the app; now based on streams

.vscode/launch.json

@@ -10,8 +10,8 @@
       "env":{
         "SLIDESHOW_ADDRESS": "0.0.0.0",
         "SLIDESHOW_PORT": "3000",
-        "SLIDESHOW_DIRECTORY": "/home/velvettear/images",
+        "SLIDESHOW_DIRECTORY": "/mnt/images",
-        "SLIDESHOW_SCANINTERVAL": "10",
+        "SLIDESHOW_SCANINTERVAL": "600",
         "SLIDESHOW_RESOLUTION": "600x1024",
         "SLIDESHOW_LOGLEVEL": "debug",
         "SLIDESHOW_PALETTE_ALGORITHM": "wsm",

README.md

@@ -22,7 +22,7 @@ configuration is entirely done via environment variables.
 | SLIDESHOW_LOGLEVEL          | "info"            | the log level                                              |
 
 **note:**  
-if `SLIDESHOW_RESOLUTION` is unset the images will served as they are (without any scaling).  
+if `SLIDESHOW_RESOLUTION` is unset or imagemagick's `convert` command is not in your `$PATH` the images will served as they are (without any scaling).  
 
 **available log levels:**
 

internal/api/response.go

@@ -0,0 +1,37 @@
+package api
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"git.velvettear.de/velvettear/loggo"
+)
+
+// struct for server responses
+type response struct {
+	StatusCode int
+	Content    interface{}
+	error      error
+}
+
+// send a response
+func (response *response) send(writer http.ResponseWriter) {
+	if response.StatusCode <= 0 {
+		if response.error != nil {
+			response.StatusCode = 500
+		} else {
+			response.StatusCode = 200
+		}
+	}
+	if response.error != nil {
+		response.Content = response.error.Error()
+	}
+	data, error := json.Marshal(response)
+	if error != nil {
+		loggo.Error("encountered an error marshalling a json response", error.Error())
+		response.StatusCode = 500
+		return
+	}
+	writer.WriteHeader(response.StatusCode)
+	writer.Write(data)
+}

internal/api/server.go

@@ -1,9 +1,10 @@
 package api
 
 import (
-	"encoding/json"
 	"net/http"
 	"strconv"
+	"strings"
+	"time"
 
 	"git.velvettear.de/velvettear/loggo"
 	"git.velvettear.de/velvettear/slideshow-api/internal"
@@ -23,42 +24,47 @@ func Run() {
 
 // register the handlers
 func registerHandlers() {
-	http.HandleFunc("/", handleImageRequest)
+	http.HandleFunc("/", serveRandomImageName)
+	http.HandleFunc("/image/", serveImage)
+	http.HandleFunc("/palette/", servePalette)
 }
 
-// handle the request to '/image'
+// request url: '/' - serve the name of a random image
-func handleImageRequest(writer http.ResponseWriter, request *http.Request) {
+func serveRandomImageName(writer http.ResponseWriter, request *http.Request) {
-	if !internal.HasFoundImages() {
+	timestamp := time.Now().UnixMilli()
-		writer.WriteHeader(404)
+	var response response
-		return
+	response.Content, response.error = internal.GetRandomImage()
+	if response.error != nil {
+		response.StatusCode = 404
 	}
-	name, data, error := internal.GetRandomImage()
+	response.send(writer)
+	loggo.DebugTimed("served random image '"+response.Content.(string)+"'", timestamp)
+}
+
+// request url: '/image' - serve an image
+func serveImage(writer http.ResponseWriter, request *http.Request) {
+	var response response
+	image, _ := strings.CutPrefix(request.URL.Path, "/image/")
+	image, error := internal.GetImagePath(image)
 	if error != nil {
-		loggo.Error("encountered an error getting a random image", error.Error())
+		response.error = error
-		writer.WriteHeader(501)
+		response.StatusCode = 404
-		writer.Write([]byte("encountered an internal server error (" + error.Error() + ")\n"))
+		response.send(writer)
 		return
 	}
-	palette, error := internal.GetColorPalette(data)
+	streamImage(writer, image)
+}
+
+// request url: '/palette' - serve the color palette of an image
+func servePalette(writer http.ResponseWriter, request *http.Request) {
+	var response response
+	image, _ := strings.CutPrefix(request.URL.Path, "/palette/")
+	image, error := internal.GetImagePath(image)
 	if error != nil {
-		writer.WriteHeader(501)
+		response.error = error
-		writer.Write([]byte("encountered an internal server error (" + error.Error() + ")\n"))
+		response.StatusCode = 404
+		response.send(writer)
 		return
 	}
-	bytes, error := json.Marshal(struct {
+	streamColorPalette(writer, image)
-		Name    string
-		Palette string
-		Data    []byte
-	}{
-		name,
-		palette,
-		data,
-	})
-	if error != nil {
-		loggo.Error("encountered an error marshalling the json response", error.Error())
-		writer.WriteHeader(501)
-		writer.Write([]byte("encountered an internal server error (" + error.Error() + ")\n"))
-		return
-	}
-	writer.Write(bytes)
 }

internal/api/stream.go

@@ -0,0 +1,124 @@
+package api
+
+import (
+	"errors"
+	"io"
+	"net/http"
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+	"time"
+
+	"git.velvettear.de/velvettear/loggo"
+	"git.velvettear.de/velvettear/slideshow-api/internal"
+	"git.velvettear.de/velvettear/slideshow-api/internal/config"
+	color_thief "github.com/kennykarnama/color-thief"
+)
+
+// central streaming method for images
+func streamImage(writer http.ResponseWriter, image string) {
+	if config.IsResolutionSet() {
+		streamScaledImage(writer, image)
+		return
+	}
+	streamUnscaledImage(writer, image)
+}
+
+// stream a color palette
+func streamColorPalette(writer http.ResponseWriter, image string) {
+	timestamp := time.Now().UnixMilli()
+	var response response
+	amount := config.PaletteColors
+	colors, error := color_thief.GetPaletteFromFile(image, amount, config.PaletteAlgorithm)
+	if error != nil {
+		loggo.Error("encountered an error getting the color palette from image '"+image+"'", error.Error())
+		response.error = error
+		response.send(writer)
+		return
+	}
+	var palette string
+	for index, color := range colors {
+		if index > 0 {
+			palette += "\n"
+		}
+		tmp := strconv.Itoa(index)
+		if len(tmp) < 2 {
+			tmp = "0" + tmp
+		}
+		tmp = "SLIDESHOW_COLOR" + tmp
+		palette += tmp + "=\"" + internal.RgbToHex(color) + "\""
+	}
+	data := []byte(palette)
+	writer.Write(data)
+	loggo.InfoTimed("successfully streamed color palette for image '"+image+"'", timestamp, "size: "+internal.FormatBytes(int64(len(data))))
+}
+
+// stream an unscaled image
+func streamUnscaledImage(writer http.ResponseWriter, image string) {
+	timestamp := time.Now().UnixMilli()
+	var response response
+	file, error := os.Open(image)
+	if error != nil {
+		loggo.Error("encountered an error opening image '"+image+"' for streaming", error.Error())
+		response.error = error
+		response.send(writer)
+		return
+	}
+	defer file.Close()
+	written, error := io.Copy(writer, file)
+	if error != nil {
+		loggo.Error("encountered an error piping image '"+image+"' to stream", error.Error())
+		response.error = error
+		response.send(writer)
+		return
+	}
+	loggo.InfoTimed("successfully streamed image '"+image+"'", timestamp, "size: "+internal.FormatBytes(written))
+}
+
+// scale and stream an image
+func streamScaledImage(writer http.ResponseWriter, image string) {
+	timestamp := time.Now().UnixMilli()
+	var response response
+	cmd := exec.Command("convert", image, "-resize", config.Resolution+"^", "-gravity", "center", "-extent", config.Resolution, "-")
+	stdout, stdoutError := cmd.StdoutPipe()
+	stderr, stderrError := cmd.StderrPipe()
+	cmd.Start()
+	if stdoutError != nil {
+		loggo.Error("enountered an error opening imagemagicks's stdout pipe", stdoutError.Error())
+		response.error = stdoutError
+		response.send(writer)
+		return
+	}
+	if stderrError != nil {
+		loggo.Error("enountered an error opening imagemagicks's stderr pipe", stderrError.Error())
+		response.error = stderrError
+		response.send(writer)
+		return
+	}
+	written, copyError := io.Copy(writer, stdout)
+	if copyError != nil {
+		loggo.Error("enountered an error piping imagemagicks's output to the stream", copyError.Error())
+		response.error = copyError
+		response.send(writer)
+		return
+	}
+	if written == 0 {
+		errorBytes, stderrError := io.ReadAll(stderr)
+		if stderrError != nil {
+			loggo.Error("enountered an error reading imagemagicks's stderr", stderrError.Error())
+			response.error = stderrError
+			response.send(writer)
+			return
+		}
+		if len(errorBytes) > 0 {
+			error := errors.New(strings.TrimSpace(string(errorBytes)))
+			loggo.Error("enountered an error executing imagemagick", error.Error())
+			response.error = error
+			response.send(writer)
+			return
+		}
+	}
+	cmd.Wait()
+	loggo.InfoTimed("successfully streamed scaled image '"+image+"'", timestamp, "size: "+internal.FormatBytes(written), "resolution: "+config.Resolution)
+}

internal/cache.go

@@ -1,44 +0,0 @@
-package internal
-
-import (
-	"image/color"
-	"strconv"
-)
-
-// the internally pre buffered (and scaled) image
-var cachedImage []byte
-
-// the internally pre buffered color palette
-var cachedPalette []byte
-
-// cache an image
-func cacheImage(image []byte) {
-	cachedImage = image
-}
-
-// cache a color palette
-func cachePalette(colors []color.Color) {
-	var palette string
-	for index, color := range colors {
-		if index > 0 {
-			palette += "\n"
-		}
-		tmp := strconv.Itoa(index)
-		if len(tmp) < 2 {
-			tmp = "0" + tmp
-		}
-		tmp = "SLIDESHOW_COLOR" + tmp
-		palette += tmp + "=\"" + rgbToHex(color) + "\""
-	}
-	cachedPalette = []byte(palette)
-}
-
-// check if an image is cached
-func hasCachedImage() bool {
-	return len(cachedImage) > 0
-}
-
-// check if a color palette is cached
-func hasCachedColorPalette() bool {
-	return len(cachedPalette) > 0
-}

internal/config/config.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"os"
+	"os/exec"
 	"strconv"
 	"strings"
 	"time"
@@ -16,6 +17,7 @@ var ScanInterval time.Duration
 var Resolution string
 var PaletteAlgorithm int
 var PaletteColors int
+var BufferSize int
 
 // initialize the config
 func Initialize() {
@@ -72,6 +74,25 @@ func Initialize() {
 		tmpInt = 16
 	}
 	PaletteColors = tmpInt
+	tmpInt, _ = strconv.Atoi(os.Getenv("SLIDESHOW_BUFFERSIZE"))
+	if tmpInt <= 0 {
+		tmpInt = 4096
+	}
+	BufferSize = tmpInt
+	if IsResolutionSet() {
+		checkForConvert()
+	}
+}
+
+// check if 'convert' is available
+func checkForConvert() {
+	cmd := exec.Command("convert")
+	error := cmd.Run()
+	if error == nil {
+		return
+	}
+	Resolution = ""
+	loggo.Warning("could not find imagemagick's 'convert' command, no scaling will be done", error.Error())
 }
 
 // check if a resolution has been specified

internal/formatter.go

@@ -0,0 +1,27 @@
+package internal
+
+import (
+	"fmt"
+	"image/color"
+	"strconv"
+)
+
+// format bytes
+func FormatBytes(bytes int64) string {
+	value := float64(bytes)
+	unit := "bytes"
+	if bytes > 1000000 {
+		value = value / 1000000
+		unit = "mega" + unit
+	} else if bytes > 1000 {
+		value = value / 1000
+		unit = "kilo" + unit
+	}
+	return strconv.FormatFloat(value, 'f', 2, 64) + " " + unit
+}
+
+// parse rgb color values to a hex hex
+func RgbToHex(color color.Color) string {
+	r, g, b, _ := color.RGBA()
+	return fmt.Sprintf("#%02x%02x%02x", uint8(r>>8), uint8(g>>8), uint8(b>>8))
+}

internal/scale.go

@@ -1,43 +0,0 @@
-package internal
-
-import (
-	"errors"
-	"io"
-	"os/exec"
-	"strings"
-	"time"
-
-	"git.velvettear.de/velvettear/loggo"
-	"git.velvettear.de/velvettear/slideshow-api/internal/config"
-)
-
-// scale an image
-func ScaleImage(image string) ([]byte, error) {
-	timestamp := time.Now().UnixMilli()
-	cmd := exec.Command("convert", image, "-resize", config.Resolution+"^", "-gravity", "center", "-extent", config.Resolution, "-")
-	stdout, stdoutError := cmd.StdoutPipe()
-	stderr, stderrError := cmd.StderrPipe()
-	var data []byte
-	cmd.Start()
-	if stdoutError != nil {
-		return data, stdoutError
-	}
-	if stderrError != nil {
-		return data, stdoutError
-	}
-	data, stdoutError = io.ReadAll(stdout)
-	if stdoutError != nil {
-		return data, stdoutError
-	}
-	errorBytes, stderrError := io.ReadAll(stderr)
-	if stderrError != nil {
-		return data, stdoutError
-	}
-	cmd.Wait()
-	errorMessage := strings.TrimSpace(string(errorBytes))
-	if len(errorMessage) > 0 {
-		return data, errors.New(errorMessage)
-	}
-	loggo.DebugTimed("successfully scaled image", timestamp, "image: "+image, "resolution: "+config.Resolution)
-	return data, nil
-}

internal/scanner.go

@@ -4,7 +4,6 @@ import (
 	"errors"
 	"io/fs"
 	"math/rand"
-	"os"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -14,17 +13,18 @@ import (
 	"git.velvettear.de/velvettear/slideshow-api/internal/config"
 )
 
-// slice of images
+// map of images
-var images []string
+var images map[string]string
 
-// temporary slice of images
+// temporary map of images
-var tmpImages []string
+var tmpImages map[string]string
 
 // Scan the specified directory
 func Scan() {
 	timestamp := time.Now()
 	directory := config.Directory
 	loggo.Info("scanning directory for images and subdirectories...", "interval: "+strconv.FormatFloat(config.ScanInterval.Seconds(), 'f', 0, 64)+" seconds", "directory: "+directory)
+	tmpImages = make(map[string]string)
 	filepath.WalkDir(directory, checkDirectory)
 	images = tmpImages
 	tmpImages = nil
@@ -32,26 +32,33 @@ func Scan() {
 	go scheduleRescan()
 }
 
-// check if images has been found
+// get a random image
-func HasFoundImages() bool {
+func GetRandomImage() (string, error) {
-	return len(images) > 0
+	if len(images) == 0 {
+		return "", errors.New("no images have been found in directory '" + config.Directory + "'")
+	}
+	random := rand.Intn(len(images))
+	index := 0
+	for key := range images {
+		if index == random {
+			return key, nil
+		}
+		index++
+	}
+	return "", errors.New("could not find a random image with index '" + strconv.Itoa(random) + "'")
 }
 
-// get a random image
+// get the path of an image by name
-func GetRandomImage() (string, []byte, error) {
+func GetImagePath(name string) (string, error) {
-	var name string
+	var path string
-	var data []byte
+	if len(name) == 0 {
-	var error error
+		return path, errors.New("no image name provided")
-	if len(images) == 0 {
-		return name, data, errors.New("no images have been found")
 	}
-	image := images[rand.Intn(len(images))]
+	image := images[name]
-	if config.IsResolutionSet() {
+	if len(image) == 0 {
-		data, error = ScaleImage(image)
+		return path, errors.New("could not find image '" + name + "' in internal map")
-	} else {
-		data, error = os.ReadFile(image)
 	}
-	return image, data, error
+	return image, nil
 }
 
 // sleep the specified interval and then trigger a rescan of the specified directory
@@ -61,7 +68,7 @@ func scheduleRescan() {
 	Scan()
 }
 
-// add image files to the slice of images and subdirectoies to the watcher
+// add image files to the map of images
 func checkDirectory(path string, dir fs.DirEntry, err error) error {
 	if err != nil {
 		return err
@@ -69,8 +76,8 @@ func checkDirectory(path string, dir fs.DirEntry, err error) error {
 	if dir.IsDir() || !isImage(path) {
 		return nil
 	}
-	tmpImages = append(tmpImages, path)
+	tmpImages[filepath.Base(path)] = path
-	loggo.Debug("added image to temporary slice of images", path)
+	loggo.Debug("added image to temporary map of images", path)
 	return nil
 }