moved scaling of images from a fixed value to a query parameter

.vscode/launch.json

@@ -10,9 +10,8 @@
       "env":{
         "SLIDESHOW_ADDRESS": "0.0.0.0",
         "SLIDESHOW_PORT": "3000",
-        "SLIDESHOW_DIRECTORY": "/mnt/images",
+        "SLIDESHOW_DIRECTORY": "/home/velvettear/images",
         "SLIDESHOW_SCANINTERVAL": "600",
-        "SLIDESHOW_RESOLUTION": "600x1024",
         "SLIDESHOW_LOGLEVEL": "debug",
         "SLIDESHOW_PALETTE_ALGORITHM": "wsm",
         "SLIDESHOW_PALETTE_COLORS": "16"

README.md

@@ -4,7 +4,13 @@ a simple web server serving (scaled) images and color palettes for [slideshow](h
 
 ## requirements
 
-- [ImageMagick](https://imagemagick.org/) (optional)
+- [ImageMagick](https://imagemagick.org/) (optional; for scaling)
+
+## endpoints
+
+- `/`: request the name of a random image
+- `/image/<name-of-an-image.jpeg>[?resolution=1920x1080]`: request the named image (in the specified resolution)
+- `/palette/<name-of-an-image.jpeg>`: request the color palette of the named image
 
 ## configuration
 
@@ -16,13 +22,12 @@ configuration is entirely done via environment variables.
 | SLIDESHOW_PORT              | 3000              | the port of the web server                                 |
 | SLIDESHOW_DIRECTORY         | "$HOME"           | path to a directory containing images                      |
 | SLIDESHOW_SCANINTERVAL      | 60                | the interval for directory scans in seconds                |
-| SLIDESHOW_RESOLUTION        |                   | the resolution to which images are scaled (i.e. 1920x1080) | 
 | SLIDESHOW_PALETTE_ALGORITHM | "wsm"             | the algorithm used to generate the color palette           |
 | SLIDESHOW_PALETTE_COLORS    | 16                | the amount of colors generated                             |
 | SLIDESHOW_LOGLEVEL          | "info"            | the log level                                              |
 
 **note:**  
-if `SLIDESHOW_RESOLUTION` is unset or imagemagick's `convert` command is not in your `$PATH` the images will served as they are (without any scaling).  
+if imagemagick's `convert` command is not in your `$PATH` the images will **not** be scaled.  
 
 **available log levels:**
 

internal/api/server.go

@@ -52,7 +52,7 @@ func serveImage(writer http.ResponseWriter, request *http.Request) {
 		response.send(writer)
 		return
 	}
-	streamImage(writer, image)
+	streamImage(writer, image, request.URL.Query().Get("resolution"))
 }
 
 // request url: '/palette' - serve the color palette of an image

internal/api/stream.go

@@ -17,9 +17,9 @@ import (
 )
 
 // central streaming method for images
-func streamImage(writer http.ResponseWriter, image string) {
+func streamImage(writer http.ResponseWriter, image string, resolution string) {
-	if config.IsResolutionSet() {
+	if config.ConvertAvailable && config.IsValidResolution(resolution) {
-		streamScaledImage(writer, image)
+		streamScaledImage(writer, image, resolution)
 		return
 	}
 	streamUnscaledImage(writer, image)
@@ -77,10 +77,10 @@ func streamUnscaledImage(writer http.ResponseWriter, image string) {
 }
 
 // scale and stream an image
-func streamScaledImage(writer http.ResponseWriter, image string) {
+func streamScaledImage(writer http.ResponseWriter, image string, resolution string) {
 	timestamp := time.Now().UnixMilli()
 	var response response
-	cmd := exec.Command("convert", image, "-resize", config.Resolution+"^", "-gravity", "center", "-extent", config.Resolution, "-")
+	cmd := exec.Command("convert", image, "-resize", resolution+"^", "-gravity", "center", "-extent", resolution, "-")
 	stdout, stdoutError := cmd.StdoutPipe()
 	stderr, stderrError := cmd.StderrPipe()
 	cmd.Start()
@@ -120,5 +120,5 @@ func streamScaledImage(writer http.ResponseWriter, image string) {
 		}
 	}
 	cmd.Wait()
-	loggo.InfoTimed("successfully streamed scaled image '"+image+"'", timestamp, "size: "+internal.FormatBytes(written), "resolution: "+config.Resolution)
+	loggo.InfoTimed("successfully streamed scaled image '"+image+"'", timestamp, "size: "+internal.FormatBytes(written), "resolution: "+resolution)
 }

internal/config/config.go

@@ -14,10 +14,10 @@ var ServerAddress string
 var ServerPort int
 var Directory string
 var ScanInterval time.Duration
-var Resolution string
 var PaletteAlgorithm int
 var PaletteColors int
 var BufferSize int
+var ConvertAvailable bool
 
 // initialize the config
 func Initialize() {
@@ -48,21 +48,6 @@ func Initialize() {
 		tmpInt = 60
 	}
 	ScanInterval = time.Duration(tmpInt) * time.Second
-	Resolution = os.Getenv("SLIDESHOW_RESOLUTION")
-	if len(Resolution) > 0 {
-		width, height, found := strings.Cut(Resolution, "x")
-		if !found {
-			loggo.Fatal("encountered an error parsing the configured resolution, make sure to specify the format like '1920x1080'")
-		}
-		_, error = strconv.Atoi(width)
-		if error != nil {
-			loggo.Fatal("encountered an error parsing the configured width '" + width + "'")
-		}
-		_, error = strconv.Atoi(height)
-		if error != nil {
-			loggo.Fatal("encountered an error parsing the configured height '" + height + "'")
-		}
-	}
 	tmpString := os.Getenv("SLIDESHOW_PALETTE_ALGORITHM")
 	if strings.ToLower(tmpString) == "wu" {
 		PaletteAlgorithm = 0
@@ -79,23 +64,33 @@ func Initialize() {
 		tmpInt = 4096
 	}
 	BufferSize = tmpInt
-	if IsResolutionSet() {
+	checkConvertCommand()
-		checkForConvert()
-	}
 }
 
 // check if 'convert' is available
-func checkForConvert() {
+func checkConvertCommand() {
-	cmd := exec.Command("convert")
+	cmd := exec.Command("which", "convert")
 	error := cmd.Run()
+	ConvertAvailable = error == nil
 	if error == nil {
 		return
 	}
-	Resolution = ""
+	loggo.Warning("could not find imagemagick's 'convert' command, scaling is unavailable", error.Error())
-	loggo.Warning("could not find imagemagick's 'convert' command, no scaling will be done", error.Error())
 }
 
-// check if a resolution has been specified
+// check if the given string is a valid resolution
-func IsResolutionSet() bool {
+func IsValidResolution(resolution string) bool {
-	return len(Resolution) > 0
+	if len(resolution) <= 0 {
+		return false
+	}
+	width, height, found := strings.Cut(resolution, "x")
+	if !found {
+		return false
+	}
+	_, error := strconv.Atoi(width)
+	if error != nil {
+		return false
+	}
+	_, error = strconv.Atoi(height)
+	return error == nil
 }

internal/palette.go

@@ -1,65 +0,0 @@
-package internal
-
-import (
-	"bytes"
-	"fmt"
-	"image"
-	"image/color"
-	"strconv"
-	"time"
-
-	"git.velvettear.de/velvettear/loggo"
-	"git.velvettear.de/velvettear/slideshow-api/internal/config"
-	color_thief "github.com/kennykarnama/color-thief"
-)
-
-// extract the given amount of dominant colors of raw image bytes
-func GetColorPalette(data []byte) (string, error) {
-	var palette string
-	timestamp := time.Now().UnixMilli()
-	amount := config.PaletteColors
-	img, _, error := image.Decode(bytes.NewReader(data))
-	if error != nil {
-		loggo.ErrorTimed("encountered an error decoding the provided raw image bytes to an image", timestamp, error.Error())
-		return palette, error
-	}
-	colors, error := color_thief.GetPalette(img, amount, config.PaletteAlgorithm)
-	if error != nil {
-		loggo.ErrorTimed("encountered an error generating the color palette from raw image bytes", timestamp, "colors: "+strconv.Itoa(amount))
-		return palette, error
-	} else {
-		loggo.DebugTimed("generated color palette from raw image bytes", timestamp, "colors: "+strconv.Itoa(amount))
-	}
-	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) + "\""
-	}
-	return palette, nil
-}
-
-// extract the given amount of dominant colors of an image
-func getColorPalette(image string) ([]color.Color, error) {
-	var colors []color.Color
-	timestamp := time.Now().UnixMilli()
-	amount := config.PaletteColors
-	colors, error := color_thief.GetPaletteFromFile(image, amount, config.PaletteAlgorithm)
-	if error != nil {
-		loggo.ErrorTimed("encountered an error generating the color palette from image", timestamp, "image: "+image, "colors: "+strconv.Itoa(amount))
-	} else {
-		loggo.DebugTimed("generated color palette from image", timestamp, "image: "+image, "colors: "+strconv.Itoa(amount))
-	}
-	return colors, error
-}
-
-// parse rgb color values to 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))
-}