Adds max scale option to prevent over-sizing

pkg/vips/bridge.go

@@ -6,6 +6,7 @@ import "C"
 import (
 	"fmt"
 	"log"
+	"math"
 	"runtime"
 	dbg "runtime/debug"
 	"unsafe"
@@ -14,6 +15,7 @@ import (
 const (
 	defaultQuality     = 90
 	defaultCompression = 6
+	maxScaleFactor     = 10
 )
 
 var stringBuffer4096 = fixedString(4096)
@@ -257,6 +259,11 @@ func vipsFlattenBackground(input *C.VipsImage, color Color) (*C.VipsImage, error
 func vipsResize(input *C.VipsImage, scale, vscale float64, kernel Kernel) (*C.VipsImage, error) {
 	incOpCounter("resize")
 	var output *C.VipsImage
+
+	// Let's not be insane
+	scale = math.Min(scale, maxScaleFactor)
+	vscale = math.Min(vscale, maxScaleFactor)
+
 	defer C.g_object_unref(C.gpointer(input))
 	if err := C.resize_image(input, &output, C.double(scale), C.double(vscale), C.int(kernel)); err != 0 {
 		return nil, handleVipsError()

pkg/vips/regression_test.go

@@ -86,6 +86,18 @@ func TestRotate(t *testing.T) {
 	})
 }
 
+func TestScale3x(t *testing.T) {
+	goldenTest(t, "../../assets/fixtures/tomatoes.png", func(tx *vips.Transform) {
+		tx.Scale(3.0)
+	})
+}
+
+func TestMaxScale(t *testing.T) {
+	goldenTest(t, "../../assets/fixtures/tomatoes.png", func(tx *vips.Transform) {
+		tx.MaxScale(1.0).ResizeWidth(100000)
+	})
+}
+
 func TestOverlay(t *testing.T) {
 	if testing.Short() {
 		return
@@ -131,11 +143,13 @@ func assertGoldenMatch(t *testing.T, file string, buf []byte) {
 		panic("bad filename")
 	}
 	name := strings.Replace(t.Name(), "/", "_", -1)
-	goldenFile := file[:i] + "." + name + ".golden" + file[i:]
+	prefix := file[:i] + "." + name
+	ext := file[i:]
+	goldenFile := prefix + ".golden" + ext
 	golden, _ := ioutil.ReadFile(goldenFile)
 	if golden != nil {
 		if !assert.Equal(t, golden, buf) {
-			failed := file[:i] + "." + name + ".failed" + file[i:]
+			failed := prefix + ".failed" + ext
 			err := ioutil.WriteFile(failed, buf, 0666)
 			if err != nil {
 				panic(err)

pkg/vips/transform.go

@@ -37,6 +37,7 @@ type TransformParams struct {
 	Height                  Scalar
 	CropOffsetX             Scalar
 	CropOffsetY             Scalar
+	MaxScale                float64
 }
 
 // Transform handles single image transformations
@@ -234,6 +235,12 @@ func (t *Transform) Scale(scale float64) *Transform {
 	return t
 }
 
+// MaxScale sets the max scale factor that this image can be enlarged or reduced by
+func (t *Transform) MaxScale(max float64) *Transform {
+	t.tx.MaxScale = max
+	return t
+}
+
 // ResizeWidth resizes the image to the given width, maintaining aspect ratio
 func (t *Transform) ResizeWidth(width int) *Transform {
 	t.tx.Width.SetInt(width)
@@ -387,6 +394,15 @@ func NewBlackboard(image *C.VipsImage, imageType ImageType, p *TransformParams)
 	bb.targetWidth = p.Width.GetRounded(imageWidth)
 	bb.targetHeight = p.Height.GetRounded(imageHeight)
 
+	if bb.MaxScale > 0 {
+		if bb.targetWidth > 0 && ratio(bb.targetWidth, imageWidth) > bb.MaxScale {
+			bb.targetWidth = int(float64(imageWidth) * bb.MaxScale)
+		}
+		if bb.targetHeight > 0 && ratio(bb.targetHeight, imageHeight) > bb.MaxScale {
+			bb.targetHeight = int(float64(imageHeight) * bb.MaxScale)
+		}
+	}
+
 	switch {
 	case bb.targetWidth > 0 && bb.targetHeight > 0:
 		// Nothing to do
@@ -407,6 +423,11 @@ func NewBlackboard(image *C.VipsImage, imageType ImageType, p *TransformParams)
 			bb.targetScale = sx
 		}
 	}
+
+	if bb.MaxScale != 0 && bb.targetScale > bb.MaxScale {
+		bb.targetScale = bb.MaxScale
+	}
+
 	return bb
 }
 
@@ -709,6 +730,10 @@ type Scalar struct {
 	Relative bool
 }
 
+func (s *Scalar) IsZero() bool {
+	return s.Value == 0 && !s.Relative
+}
+
 func (s *Scalar) SetInt(value int) {
 	s.Set(float64(value))
 }