resources/image: Fix fill with smartcrop sometimes returning 0 bytes images

Fixes #7955

resources/image.go

@@ -201,9 +201,26 @@ func (i *imageResource) Fill(spec string) (resource.Image, error) {
 		return nil, err
 	}
 
+	img, err := i.doWithImageConfig(conf, func(src image.Image) (image.Image, error) {
+		return i.Proc.ApplyFiltersFromConfig(src, conf)
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	if conf.Anchor == 0 && img.Width() == 0 || img.Height() == 0 {
+		// See https://github.com/gohugoio/hugo/issues/7955
+		// Smartcrop fails silently in some rare cases.
+		// Fall back to a center fill.
+		conf.Anchor = gift.CenterAnchor
+		conf.AnchorStr = "center"
 		return i.doWithImageConfig(conf, func(src image.Image) (image.Image, error) {
 			return i.Proc.ApplyFiltersFromConfig(src, conf)
 		})
+	}
+
+	return img, err
 }
 
 func (i *imageResource) Filter(filters ...interface{}) (resource.Image, error) {

resources/image_test.go

@@ -175,36 +175,6 @@ func TestImageTransformFormat(t *testing.T) {
 	assertFileCache(c, fileCache, path.Base(imageGif.RelPermalink()), 225, 141)
 }
 
-// https://github.com/gohugoio/hugo/issues/4261
-func TestImageTransformLongFilename(t *testing.T) {
-	c := qt.New(t)
-
-	image := fetchImage(c, "1234567890qwertyuiopasdfghjklzxcvbnm5to6eeeeee7via8eleph.jpg")
-	c.Assert(image, qt.Not(qt.IsNil))
-
-	resized, err := image.Resize("200x")
-	c.Assert(err, qt.IsNil)
-	c.Assert(resized, qt.Not(qt.IsNil))
-	c.Assert(resized.Width(), qt.Equals, 200)
-	c.Assert(resized.RelPermalink(), qt.Equals, "/a/_hu59e56ffff1bc1d8d122b1403d34e039f_90587_65b757a6e14debeae720fe8831f0a9bc.jpg")
-	resized, err = resized.Resize("100x")
-	c.Assert(err, qt.IsNil)
-	c.Assert(resized, qt.Not(qt.IsNil))
-	c.Assert(resized.Width(), qt.Equals, 100)
-	c.Assert(resized.RelPermalink(), qt.Equals, "/a/_hu59e56ffff1bc1d8d122b1403d34e039f_90587_c876768085288f41211f768147ba2647.jpg")
-}
-
-// Issue 6137
-func TestImageTransformUppercaseExt(t *testing.T) {
-	c := qt.New(t)
-	image := fetchImage(c, "sunrise.JPG")
-
-	resized, err := image.Resize("200x")
-	c.Assert(err, qt.IsNil)
-	c.Assert(resized, qt.Not(qt.IsNil))
-	c.Assert(resized.Width(), qt.Equals, 200)
-}
-
 // https://github.com/gohugoio/hugo/issues/5730
 func TestImagePermalinkPublishOrder(t *testing.T) {
 	for _, checkOriginalFirst := range []bool{true, false} {
@@ -250,6 +220,70 @@ func TestImagePermalinkPublishOrder(t *testing.T) {
 	}
 }
 
+func TestImageBugs(t *testing.T) {
+	c := qt.New(t)
+
+	// Issue #4261
+	c.Run("Transform long filename", func(c *qt.C) {
+		image := fetchImage(c, "1234567890qwertyuiopasdfghjklzxcvbnm5to6eeeeee7via8eleph.jpg")
+		c.Assert(image, qt.Not(qt.IsNil))
+
+		resized, err := image.Resize("200x")
+		c.Assert(err, qt.IsNil)
+		c.Assert(resized, qt.Not(qt.IsNil))
+		c.Assert(resized.Width(), qt.Equals, 200)
+		c.Assert(resized.RelPermalink(), qt.Equals, "/a/_hu59e56ffff1bc1d8d122b1403d34e039f_90587_65b757a6e14debeae720fe8831f0a9bc.jpg")
+		resized, err = resized.Resize("100x")
+		c.Assert(err, qt.IsNil)
+		c.Assert(resized, qt.Not(qt.IsNil))
+		c.Assert(resized.Width(), qt.Equals, 100)
+		c.Assert(resized.RelPermalink(), qt.Equals, "/a/_hu59e56ffff1bc1d8d122b1403d34e039f_90587_c876768085288f41211f768147ba2647.jpg")
+
+	})
+
+	// Issue #6137
+	c.Run("Transform upper case extension", func(c *qt.C) {
+		image := fetchImage(c, "sunrise.JPG")
+
+		resized, err := image.Resize("200x")
+		c.Assert(err, qt.IsNil)
+		c.Assert(resized, qt.Not(qt.IsNil))
+		c.Assert(resized.Width(), qt.Equals, 200)
+
+	})
+
+	// Issue #7955
+	c.Run("Fill with smartcrop", func(c *qt.C) {
+		sunset := fetchImage(c, "sunset.jpg")
+
+		for _, test := range []struct {
+			originalDimensions string
+			targetWH           int
+		}{
+			{"408x403", 400},
+			{"425x403", 400},
+			{"459x429", 400},
+			{"476x442", 400},
+			{"544x403", 400},
+			{"476x468", 400},
+			{"578x585", 550},
+			{"578x598", 550},
+		} {
+			c.Run(test.originalDimensions, func(c *qt.C) {
+				image, err := sunset.Resize(test.originalDimensions)
+				c.Assert(err, qt.IsNil)
+				resized, err := image.Fill(fmt.Sprintf("%dx%d smart", test.targetWH, test.targetWH))
+				c.Assert(err, qt.IsNil)
+				c.Assert(resized, qt.Not(qt.IsNil))
+				c.Assert(resized.Width(), qt.Equals, test.targetWH)
+				c.Assert(resized.Height(), qt.Equals, test.targetWH)
+			})
+
+		}
+
+	})
+}
+
 func TestImageTransformConcurrent(t *testing.T) {
 	var wg sync.WaitGroup
 

resources/images/smartcrop.go

@@ -15,6 +15,7 @@ package images
 
 import (
 	"image"
+	"math"
 
 	"github.com/disintegration/gift"
 
@@ -41,6 +42,14 @@ type imagingResizer struct {
 }
 
 func (r imagingResizer) Resize(img image.Image, width, height uint) image.Image {
+	// See https://github.com/gohugoio/hugo/issues/7955#issuecomment-861710681
+	scaleX, scaleY := calcFactorsNfnt(width, height, float64(img.Bounds().Dx()), float64(img.Bounds().Dy()))
+	if width == 0 {
+		width = uint(math.Ceil(float64(img.Bounds().Dx()) / scaleX))
+	}
+	if height == 0 {
+		height = uint(math.Ceil(float64(img.Bounds().Dy()) / scaleY))
+	}
 	result, _ := r.p.Filter(img, gift.Resize(int(width), int(height), r.filter))
 	return result
 }
@@ -71,3 +80,25 @@ func (p *ImageProcessor) smartCrop(img image.Image, width, height int, filter gi
 
 	return img.Bounds().Intersect(rect), nil
 }
+
+// Calculates scaling factors using old and new image dimensions.
+// Code borrowed from https://github.com/nfnt/resize/blob/83c6a9932646f83e3267f353373d47347b6036b2/resize.go#L593
+func calcFactorsNfnt(width, height uint, oldWidth, oldHeight float64) (scaleX, scaleY float64) {
+	if width == 0 {
+		if height == 0 {
+			scaleX = 1.0
+			scaleY = 1.0
+		} else {
+			scaleY = oldHeight / float64(height)
+			scaleX = scaleY
+		}
+	} else {
+		scaleX = oldWidth / float64(width)
+		if height == 0 {
+			scaleY = scaleX
+		} else {
+			scaleY = oldHeight / float64(height)
+		}
+	}
+	return
+}