Add quality option

- Added 'q' option to specify quality (used for JPEGs)
- Updated tests
- Update documentation

README.md

@@ -66,6 +66,11 @@ The `r{degrees}` option will rotate the image the specified number of degrees,
 counter-clockwise.  Valid degrees values are `90`, `180`, and `270`.  Images
 are rotated **after** being resized.
 
+#### Quality ####
+
+The `q{percentage}` option can be used to specify the output quality (JPEG
+only).
+
 #### Flip ####
 
 The `fv` option will flip the image vertically.  The `fh` option will flip the
@@ -99,6 +104,7 @@ x100    | 100px tall, proportional width           | <a href="https://willnorris
 150,fit | scale to fit 150px square, no cropping   | <a href="https://willnorris.com/api/imageproxy/150,fit/https://willnorris.com/2013/12/small-things.jpg"><img src="https://willnorris.com/api/imageproxy/150,fit/https://willnorris.com/2013/12/small-things.jpg" alt="150,fit"></a>
 100,r90 | 100px square, rotated 90 degrees         | <a href="https://willnorris.com/api/imageproxy/100,r90/https://willnorris.com/2013/12/small-things.jpg"><img src="https://willnorris.com/api/imageproxy/100,r90/https://willnorris.com/2013/12/small-things.jpg" alt="100,r90"></a>
 100,fv,fh | 100px square, flipped horizontal and vertical | <a href="https://willnorris.com/api/imageproxy/100,fv,fh/https://willnorris.com/2013/12/small-things.jpg"><img src="https://willnorris.com/api/imageproxy/100,fv,fh/https://willnorris.com/2013/12/small-things.jpg" alt="100,fv,fh"></a>
+200x,q60 | 200px wide, proportional height, 60% quality | <a href="https://willnorris.com/api/imageproxy/200x,q60/https://willnorris.com/2013/12/small-things.jpg"><img src="https://willnorris.com/api/imageproxy/200x,q60/https://willnorris.com/2013/12/small-things.jpg" alt="200x,q60"></a>
 
 
 ## Getting Started ##

data.go

@@ -28,6 +28,7 @@ const (
 	optFlipVertical   = "fv"
 	optFlipHorizontal = "fh"
 	optRotatePrefix   = "r"
+	optQualityPrefix  = "q"
 	optSizeDelimiter  = "x"
 )
 
@@ -57,6 +58,9 @@ type Options struct {
 
 	FlipVertical   bool
 	FlipHorizontal bool
+
+	// Quality of output image
+	Quality int
 }
 
 var emptyOptions = Options{}
@@ -76,6 +80,7 @@ func (o Options) String() string {
 	if o.FlipHorizontal {
 		fmt.Fprintf(buf, ",%s", optFlipHorizontal)
 	}
+	fmt.Fprintf(buf, ",%s%d", string(optQualityPrefix), o.Quality)
 	return buf.String()
 }
 
@@ -119,6 +124,11 @@ func (o Options) String() string {
 // The "fv" option will flip the image vertically. The "fh" option will flip
 // the image horizontally. Images are flipped after being rotated.
 //
+// Quality
+//
+// The "q{qualityPercentage}" option can be used to specify the quality of the
+// output file (JPEG only)
+//
 // Examples
 //
 // 	0x0       - no resizing
@@ -130,6 +140,7 @@ func (o Options) String() string {
 // 	150,fit   - scale to fit 150 pixels square, no cropping
 // 	100,r90   - 100 pixels square, rotated 90 degrees
 // 	100,fv,fh - 100 pixels square, flipped horizontal and vertical
+// 	200x,q80  - 200 pixels wide, proportional height, 80% quality
 func ParseOptions(str string) Options {
 	options := Options{}
 
@@ -146,6 +157,9 @@ func ParseOptions(str string) Options {
 		case strings.HasPrefix(opt, optRotatePrefix):
 			value := strings.TrimPrefix(opt, optRotatePrefix)
 			options.Rotate, _ = strconv.Atoi(value)
+		case strings.HasPrefix(opt, optQualityPrefix):
+			value := strings.TrimPrefix(opt, optQualityPrefix)
+			options.Quality, _ = strconv.Atoi(value)
 		case strings.Contains(opt, optSizeDelimiter):
 			size := strings.SplitN(opt, optSizeDelimiter, 2)
 			if w := size[0]; w != "" {

data_test.go

@@ -26,15 +26,15 @@ func TestOptions_String(t *testing.T) {
 	}{
 		{
 			emptyOptions,
-			"0x0",
+			"0x0,q0",
 		},
 		{
-			Options{1, 2, true, 90, true, true},
+			Options{1, 2, true, 90, true, true, 80},
-			"1x2,fit,r90,fv,fh",
+			"1x2,fit,r90,fv,fh,q80",
 		},
 		{
-			Options{0.15, 1.3, false, 45, false, false},
+			Options{0.15, 1.3, false, 45, false, false, 95},
-			"0.15x1.3,r45",
+			"0.15x1.3,r45,q95",
 		},
 	}
 
@@ -82,8 +82,8 @@ func TestParseOptions(t *testing.T) {
 		{"FOO,1,BAR,r90,BAZ", Options{Width: 1, Height: 1, Rotate: 90}},
 
 		// all flags, in different orders
-		{"1x2,fit,r90,fv,fh", Options{1, 2, true, 90, true, true}},
+		{"q70,1x2,fit,r90,fv,fh", Options{1, 2, true, 90, true, true, 70}},
-		{"r90,fh,1x2,fv,fit", Options{1, 2, true, 90, true, true}},
+		{"r90,fh,q90,1x2,fv,fit", Options{1, 2, true, 90, true, true, 90}},
 	}
 
 	for _, tt := range tests {

transform.go

@@ -53,7 +53,13 @@ func Transform(img []byte, opt Options) ([]byte, error) {
 	case "gif":
 		gif.Encode(buf, m, nil)
 	case "jpeg":
-		jpeg.Encode(buf, m, &jpeg.Options{Quality: jpegQuality})
+		quality := opt.Quality
+
+		if quality == 0 {
+			quality = jpegQuality
+		}
+
+		jpeg.Encode(buf, m, &jpeg.Options{Quality: quality})
 	case "png":
 		png.Encode(buf, m)
 	}