#101 Limit min width to original image width

The first implementation of the min width parameter did not care about whether the original image could actually support a crop of this size. The resulting image min width now is capped by the original image min width. If one needs to have a bigger resulting image it needs to be combined with a resize filter.

filters/cropbyfocalpoint.go

@@ -17,6 +17,13 @@ type cropByFocalPoint struct {
 	minWidth	int
 }
 
+func Min(x, y int) int {
+	if x < y {
+		return x
+	}
+	return y
+}
+
 // NewCropByFocalPoint creates a new filter of this type
 func NewCropByFocalPoint() filters.Spec {
 	return &cropByFocalPoint{}
@@ -57,10 +64,10 @@ func (f *cropByFocalPoint) CreateOptions(imageContext *ImageFilterContext) (*bim
 	if f.minWidth != -1 {
 		minHeight := int(f.aspectRatio * float64(f.minWidth))
 
-		minX := int(float64(f.minWidth) * f.targetX)
-		maxX := imageSize.Width - int(float64(f.minWidth) * (1 - f.targetX))
-		minY := int(float64(minHeight) * f.targetY)
-		maxY := imageSize.Height - int(float64(minHeight) * (1 - f.targetY))
+		minX := int(float64(Min(f.minWidth, imageSize.Width)) * f.targetX)
+		maxX := imageSize.Width - int(float64(Min(f.minWidth, imageSize.Width)) * (1 - f.targetX))
+		minY := int(float64(Min(minHeight, imageSize.Height)) * f.targetY)
+		maxY := imageSize.Height - int(float64(Min(minHeight, imageSize.Height)) * (1 - f.targetY))
 
 		if x < minX {
 			x = minX

filters/cropbyfocalpoint_test.go

@@ -70,6 +70,24 @@ func TestCropByFocalPoint_CreateOptions_MinWidth(t *testing.T) {
 	assert.Equal(t, 250, options.AreaHeight)
 	assert.Equal(t, 209, options.Top)
 	assert.Equal(t, 0, options.Left)
+
+	c = cropByFocalPoint{targetX: 0.5, targetY: 0.5, aspectRatio: 0.5, minWidth: 1500.0}
+
+	options, _ = c.CreateOptions(buildParameters(fc, image))
+
+	assert.Equal(t, 1000, options.AreaWidth)
+	assert.Equal(t, 500, options.AreaHeight)
+	assert.Equal(t, 84, options.Top)
+	assert.Equal(t, 0, options.Left)
+
+	c = cropByFocalPoint{targetX: 0.5, targetY: 0.5, aspectRatio: 1.0, minWidth: 1500.0}
+
+	options, _ = c.CreateOptions(buildParameters(fc, image))
+
+	assert.Equal(t, 668, options.AreaWidth)
+	assert.Equal(t, 668, options.AreaHeight)
+	assert.Equal(t, 0, options.Top)
+	assert.Equal(t, 166, options.Left)
 }
 
 func TestCropByFocalPoint_CreateOptions_MissingPathParam(t *testing.T) {