Add TrimBackground as an argument + go.mod + fix pointer bug [Proposal]

go.mod

@@ -0,0 +1,3 @@
+module github.com/goatapp/bimg
+
+go 1.17

image_test.go

@@ -533,28 +533,102 @@ func TestImageTrim(t *testing.T) {
 }
 
 func TestImageTrimParameters(t *testing.T) {
+	t.Run("When trim parameters include Background", func(t *testing.T) {
+		if !(VipsMajorVersion >= 8 && VipsMinorVersion >= 6) {
+			t.Skipf("Skipping this test, libvips doesn't meet version requirement %s >= 8.6", VipsVersion)
+		}
 
-	if !(VipsMajorVersion >= 8 && VipsMinorVersion >= 6) {
-		t.Skipf("Skipping this test, libvips doesn't meet version requirement %s >= 8.6", VipsVersion)
-	}
+		i := initImage("test.png")
+		options := Options{
+			Trim:       true,
+			Background: Color{0.0, 0.0, 0.0},
+			Threshold:  10.0,
+		}
+		buf, err := i.Process(options)
+		if err != nil {
+			t.Errorf("Cannot process the image: %#v", err)
+		}
 
-	i := initImage("test.png")
-	options := Options{
-		Trim:       true,
-		Background: Color{0.0, 0.0, 0.0},
-		Threshold:  10.0,
-	}
-	buf, err := i.Process(options)
-	if err != nil {
-		t.Errorf("Cannot process the image: %#v", err)
-	}
+		err = assertSize(buf, 400, 257)
+		if err != nil {
+			t.Errorf("The image wasn't trimmed. %s", err)
+		}
 
-	err = assertSize(buf, 400, 257)
-	if err != nil {
-		t.Errorf("The image wasn't trimmed.")
-	}
+		Write("testdata/parameter_trim.png", buf)
+	})
+	t.Run("When trim parameters include TrimBackground Transparent PNG", func(t *testing.T) {
+		if !(VipsMajorVersion >= 8 && VipsMinorVersion >= 6) {
+			t.Skipf("Skipping this test, libvips doesn't meet version requirement %s >= 8.6", VipsVersion)
+		}
 
-	Write("testdata/parameter_trim.png", buf)
+		i := initImage("transparent.png")
+		options := Options{
+			Trim:           true,
+			TrimBackground: Color{0, 0, 0},
+			Threshold:      10.0,
+		}
+		buf, err := i.Process(options)
+		if err != nil {
+			t.Errorf("Cannot process the image: %#v", err)
+		}
+
+		err = assertSize(buf, 247, 206)
+		if err != nil {
+			t.Errorf("The image wasn't trimmed. %s", err)
+		}
+
+		Write("testdata/trim_background.png", buf)
+	})
+	t.Run("When trim parameters include TrimBackground Background JPEG", func(t *testing.T) {
+		if !(VipsMajorVersion >= 8 && VipsMinorVersion >= 6) {
+			t.Skipf("Skipping this test, libvips doesn't meet version requirement %s >= 8.6", VipsVersion)
+		}
+
+		i := initImage("test_1000_yeezy_additional_photo.jpeg")
+		options := Options{
+			Trim:           true,
+			TrimBackground: Color{255, 255, 255},
+			Threshold:      20.0,
+		}
+		buf, err := i.Process(options)
+		if err != nil {
+			t.Errorf("Cannot process the image: %#v", err)
+		}
+
+		err = assertSize(buf, 535, 274)
+		if err != nil {
+			t.Errorf("The image wasn't trimmed. %s", err)
+		}
+
+		Write("testdata/trimmed_product_additional_photo.jpeg", buf)
+	})
+	t.Run("When trim parameters include TrimBackground Background And Padding", func(t *testing.T) {
+		if !(VipsMajorVersion >= 8 && VipsMinorVersion >= 6) {
+			t.Skipf("Skipping this test, libvips doesn't meet version requirement %s >= 8.6", VipsVersion)
+		}
+
+		i := initImage("test_1000_yeezy_additional_photo.jpeg")
+		options := Options{
+			Trim:           true,
+			TrimBackground: Color{255, 255, 255},
+			Threshold:      20.0,
+			TrimPaddingPercent: TrimPaddingPercent{
+				X: 1,
+				Y: 1,
+			},
+		}
+		buf, err := i.Process(options)
+		if err != nil {
+			t.Errorf("Cannot process the image: %#v", err)
+		}
+
+		err = assertSize(buf, 545, 288)
+		if err != nil {
+			t.Errorf("The image wasn't trimmed. %s", err)
+		}
+
+		Write("testdata/trimmed_product_additional_photo_padded.jpeg", buf)
+	})
 }
 
 func TestImageLength(t *testing.T) {

options.go

@@ -170,6 +170,12 @@ type WatermarkImage struct {
 	Opacity float32
 }
 
+// represents percentage of padding on an image trim extract
+type TrimPaddingPercent struct {
+	X int
+	Y int
+}
+
 // GaussianBlur represents the gaussian image transformation values.
 type GaussianBlur struct {
 	Sigma   float64
@@ -228,6 +234,10 @@ type Options struct {
 	Palette        bool
 	// Speed defines the AVIF encoders CPU effort. Valid values are 0-8.
 	Speed int
+	// color of the background when trimming an alpha based image
+	TrimBackground Color
+
+	TrimPaddingPercent TrimPaddingPercent
 
 	// private fields
 	autoRotateOnly bool

resizer.go

@@ -300,8 +300,16 @@ func extractOrEmbedImage(image *C.VipsImage, o Options) (*C.VipsImage, error) {
 		image, err = vipsEmbed(image, left, top, o.Width, o.Height, o.Extend, o.Background)
 		break
 	case o.Trim:
-		left, top, width, height, err := vipsTrim(image, o.Background, o.Threshold)
+		// keeps compatibility with old APIs that only use Background
+		if o.TrimBackground == ColorBlack {
+			o.TrimBackground = o.Background
+		}
+		left, top, width, height, err := vipsTrim(image, o.TrimBackground, o.Threshold)
 		if err == nil {
+			if o.TrimPaddingPercent.X > 0 || o.TrimPaddingPercent.Y > 0 {
+				left, top, width, height = calculatePadding(left, top, width, height, inWidth, inHeight, o.TrimPaddingPercent)
+			}
+
 			image, err = vipsExtract(image, left, top, width, height)
 		}
 		break
@@ -553,6 +561,26 @@ func calculateCrop(inWidth, inHeight, outWidth, outHeight int, gravity Gravity)
 	return left, top
 }
 
+func calculatePadding(inLeft, inTop, areaWidth, areaHeight, inWidth, inHeight int, trimPaddingPercent TrimPaddingPercent) (int, int, int, int) {
+	top := inTop
+	left := inLeft
+	width := areaWidth
+	height := areaHeight
+	if trimPaddingPercent.X > 0 {
+		paddingPercent := (float64(trimPaddingPercent.X) / 100)
+		xBorder := math.Round(float64(areaWidth) * paddingPercent)
+		left = int(math.Max(0, float64(inLeft)-xBorder))
+		width = int(math.Min(float64(inWidth)-float64(inLeft), float64(areaWidth)+2*xBorder))
+	}
+	if trimPaddingPercent.Y > 0 {
+		paddingPercent := (float64(trimPaddingPercent.Y) / 100)
+		yBorder := math.Round(float64(inHeight) * paddingPercent)
+		top = int(math.Max(0, float64(inTop)-yBorder))
+		height = int(math.Min(float64(inHeight)-float64(inTop), float64(areaHeight)+2*yBorder))
+	}
+	return left, top, width, height
+}
+
 func calculateRotationAndFlip(image *C.VipsImage, angle Angle) (Angle, bool) {
 	rotate := D0
 	flip := false

vips.go

@@ -594,7 +594,6 @@ func vipsSmartCrop(image *C.VipsImage, width, height int) (*C.VipsImage, error)
 }
 
 func vipsTrim(image *C.VipsImage, background Color, threshold float64) (int, int, int, int, error) {
-	defer C.g_object_unref(C.gpointer(image))
 
 	top := C.int(0)
 	left := C.int(0)