Respond to comments

plotter/colorbar_test.go

@@ -5,6 +5,7 @@
 package plotter
 
 import (
+	"image/color"
 	"log"
 	"testing"
 
@@ -41,7 +42,11 @@ func ExampleColorBar_horizontal_log() {
 	if err != nil {
 		log.Panic(err)
 	}
-	l := &ColorBar{ColorMap: moreland.ExtendedBlackBody()}
+	colorMap, err := moreland.NewLuminance([]color.Color{color.Black, color.White})
+	if err != nil {
+		log.Panic(err)
+	}
+	l := &ColorBar{ColorMap: colorMap}
 	l.ColorMap.SetMin(1)
 	l.ColorMap.SetMax(100)
 	p.Add(l)

plotter/image.go

@@ -56,7 +56,7 @@ func (img *Image) Plot(c draw.Canvas, p *plot.Plot) {
 		Min: vg.Point{X: xmin, Y: ymin},
 		Max: vg.Point{X: xmax, Y: ymax},
 	}
-	c.DrawImage(rect, img.transform(p))
+	c.DrawImage(rect, img.transformFor(p))
 }
 
 // DataRange implements the DataRange method
@@ -72,7 +72,7 @@ func (img *Image) GlyphBoxes(plt *plot.Plot) []plot.GlyphBox {
 }
 
 // transform warps the image to align with non-linear axes.
-func (img *Image) transform(p *plot.Plot) image.Image {
+func (img *Image) transformFor(p *plot.Plot) image.Image {
 	_, xLinear := p.X.Scale.(plot.LinearScale)
 	_, yLinear := p.Y.Scale.(plot.LinearScale)
 	if xLinear && yLinear {
@@ -81,21 +81,24 @@ func (img *Image) transform(p *plot.Plot) image.Image {
 	b := img.img.Bounds()
 	o := image.NewNRGBA64(b)
 	for c := 0; c < img.cols; c++ {
+		// Find the equivalent image column after applying axis transforms.
+		cTrans := int(p.X.Norm(img.x(c)) * float64(img.cols))
+		// Find the equivalent column of the previous image column after applying
+		// axis transforms.
+		cPrevTrans := int(p.X.Norm(img.x(maxInt(c-1, 0))) * float64(img.cols))
 		for r := 0; r < img.rows; r++ {
-			// Find the equivalent image row and column after applying
-			// the axis transforms.
-			cTrans := int(p.X.Norm(img.x(c)) * float64(img.cols))
+			// Find the equivalent image row after applying axis transforms.
 			rTrans := int(p.Y.Norm(img.y(r)) * float64(img.rows))
-			// Find the equivalent row and column of the previous image row
-			// and column after applying the axis transforms.
-			cPrevTrans := int(p.X.Norm(img.x(maxInt(c-1, 0))) * float64(img.cols))
+			// Find the equivalent row of the previous image row after applying
+			// axis transforms.
 			rPrevTrans := int(p.Y.Norm(img.y(maxInt(r-1, 0))) * float64(img.rows))
-			crColor := img.img.At(c, r)
+			crColor := img.img.At(c, img.rows-r-1)
 			// Set all the pixels in the new image between (cPrevTrans, rPrevTrans)
 			// and (cTrans, rTrans) to the color at (c,r) in the original image.
+			// TODO: Improve interpolation.
 			for cPrime := cPrevTrans; cPrime <= cTrans; cPrime++ {
 				for rPrime := rPrevTrans; rPrime <= rTrans; rPrime++ {
-					o.Set(cPrime, rPrime, crColor)
+					o.Set(cPrime, img.rows-rPrime-1, crColor)
 				}
 			}
 		}

plotter/image_test.go

@@ -63,7 +63,7 @@ func ExampleImage_log() {
 	p.Title.Text = "A Logo"
 
 	// load an image
-	f, err := os.Open("testdata/image_plot_input.png")
+	f, err := os.Open("../../gonum/gopher.png")
 	if err != nil {
 		log.Fatalf("error opening image file: %v\n", err)
 	}