The old code.google.com repo will be deleted. The github draw2d repo has now also a new pdf backend. You can use this to generate with the same draw2d code pdf charts.

For a demo pdf output see:

• https://raw.githubusercontent.com/llgcode/draw2d/master/resource/image/geometry.pdf
• https://raw.githubusercontent.com/llgcode/draw2d/master/resource/image/postscript.pdf

At the moment if you tried to diff images to see if you changed anything, you get a different image anyway due to the use of the rand package.

TIL: github has a nice visual diff

You can leave this pull request outstanding until I implement drawing "best of", if you like.

This is the last request of the day. Thanks for chart, it is really useful!

fixes https://github.com/vdobler/chart/issues/27

In the code there is now a comparison which sets the "large-arc-flag" if needed as described in the SVG documenation.

Examples of plots:

Hi,

This is just a suggestion but I recommend adding a way people can overwrite the timezone location for the TRange stuff. This is just an "example" of how I hacked it together to work for me, unfortunately I don't have a good understanding on how this library is working so it might not be the best solution.

Regards, Arran

github.com/vdobler/chart/svgg/svg.go:59: suspicious shift of sg.bg.R
github.com/vdobler/chart/svgg/svg.go:59: suspicious shift of sg.bg.G
github.com/vdobler/chart/svgg/svg.go:59: suspicious shift of sg.bg.B
github.com/vdobler/chart/svgg/svg.go:60: suspicious shift of sg.bg.A
github.com/vdobler/chart/svgg/svg.go:73: suspicious shift of sg.bg.R
github.com/vdobler/chart/svgg/svg.go:73: suspicious shift of sg.bg.G
github.com/vdobler/chart/svgg/svg.go:73: suspicious shift of sg.bg.B
github.com/vdobler/chart/svgg/svg.go:73: suspicious shift of sg.bg.A

The above locations shift color.RGBA fields right by 8 (c.R >> 8). But as they are uint8s, a right shift of 8 will always yield 0. It's not obvious what these shifts are supposed to be doing.

I'm working on an OpenGL backend for chart, and it's really obvious that some lines are composed out of lots of little lines.

Would it be possible to make a new Polygon function? Backends not implementing it yet could fall back to drawing individual lines.

If I try to install the example, I get the following error:

$ go get -v github.com/vdobler/chart/example
github.com/vdobler/chart/imgg
# github.com/vdobler/chart/imgg
github.com/vdobler/chart/imgg/image.go:101: cannot use dpi (type int) as type float64 in function argument
github.com/vdobler/chart/imgg/image.go:110: c.FUnitToFix32 undefined (type *freetype.Context has no field or method FUnitToFix32)
github.com/vdobler/chart/imgg/image.go:110: cannot use prev (type truetype.Index) as type int32 in function argument
github.com/vdobler/chart/imgg/image.go:110: not enough arguments in call to ig.font.Kerning
github.com/vdobler/chart/imgg/image.go:112: c.FUnitToFix32 undefined (type *freetype.Context has no field or method FUnitToFix32)
github.com/vdobler/chart/imgg/image.go:112: cannot use index (type truetype.Index) as type int32 in function argument
github.com/vdobler/chart/imgg/image.go:112: not enough arguments in call to ig.font.HMetric
github.com/vdobler/chart/imgg/image.go:259: cannot use dpi (type int) as type float64 in function argument
github.com/vdobler/chart/imgg/image.go:267: c.FUnitToPixelRU undefined (type *freetype.Context has no field or method FUnitToPixelRU)
github.com/vdobler/chart/imgg/image.go:267: ig.font.UnitsPerEm undefined (type *truetype.Font has no field or method UnitsPerEm)
github.com/vdobler/chart/imgg/image.go:267: too many errors

fixes https://github.com/vdobler/chart/issues/27

In the code there is now a comparison which sets the "large-arc-flag" if needed as described in the SVG documenation.

Examples of plots:

package main

import (
	"image/color"
	"image/jpeg"
	"log"
	"os"

	"github.com/vdobler/chart"
	"github.com/vdobler/chart/imgg"
)

func main() {
	style := chart.Style{Symbol: 'o', LineColor: color.NRGBA{0x00, 0x00, 0xff, 0xff},
		FillColor: color.NRGBA{0xff, 0xff, 0xff, 0xff},
		LineStyle: chart.SolidLine, LineWidth: 2}
	c := chart.BarChart{}
	c.YRange.Label = "Total"
	c.YRange.Fixed(0, 56000, 5000)
	c.AddDataPair("Total",
		[]float64{1, 2, 3, 4, 5},
		[]float64{55954, 55653, 54100, 51527, 44034}, style)
	g := imgg.New(640, 480, color.RGBA{255, 255, 255, 255}, nil, nil)
	c.Plot(g)
	fo, err := os.Create("output.jpg")
	if err != nil {
		log.Fatal(err)
	}
	defer fo.Close()
	if err = jpeg.Encode(fo, g.Image, nil); err != nil {
		log.Fatal(err)
	}
}

Result: https://i.imgur.com/5dLCgVp.jpg

Y axis: 5000 is formatted as 5.0 k unlike all the other values (10 k, not 10.0 k, etc.)

X axis: the first label is somehow 500m (?) instead of 0 or 0.0.

I am newbie to go and can't understand how to use this package. Can you please provide basic usage with some examples. Because example you provided is big and hard to understand for me :(. And when I start my own test project I have errors like this:

../../.go/src/github.com/vdobler/chart/imgg/image.go:9:2: cannot find package "github.com/golang/freetype" in any of:
    /usr/lib/go/src/github.com/golang/freetype (from $GOROOT)
    /home/kir/.go/src/github.com/golang/freetype (from $GOPATH)
../../.go/src/github.com/vdobler/chart/imgg/image.go:10:2: cannot find package "github.com/golang/freetype/truetype" in any of:
    /usr/lib/go/src/github.com/golang/freetype/truetype (from $GOROOT)
    /home/kir/.go/src/github.com/golang/freetype/truetype (from $GOPATH)
../../.go/src/github.com/vdobler/chart/imgg/image.go:11:2: cannot find package "github.com/llgcode/draw2d" in any of:
    /usr/lib/go/src/github.com/llgcode/draw2d (from $GOROOT)
    /home/kir/.go/src/github.com/llgcode/draw2d (from $GOPATH)
../../.go/src/github.com/vdobler/chart/imgg/image.go:12:2: cannot find package "github.com/llgcode/draw2d/draw2dimg" in any of:
    /usr/lib/go/src/github.com/llgcode/draw2d/draw2dimg (from $GOROOT)
    /home/kir/.go/src/github.com/llgcode/draw2d/draw2dimg (from $GOPATH)
../../.go/src/github.com/vdobler/chart/imgg/image.go:14:2: cannot find package "golang.org/x/image/draw" in any of:
    /usr/lib/go/src/golang.org/x/image/draw (from $GOROOT)
    /home/kir/.go/src/golang.org/x/image/draw (from $GOPATH)
....

Every exported function in a program should have a doc comment. The first sentence should be a summary that starts with the name being declared. From effective go.

I generated this with CodeLingo and I'm keen to get some feedback, but this is automated so feel free to close it and just say "opt out" to opt out of future CodeLingo outreach PRs.

I'm getting an "out of memory" error when trying to plot data on a logarithmic scale, but only when the data is within a certain range. Please look at the following:

https://jsfiddle.net/vp72e7j9/

If the data is above or below the range, the chart renders fine, however, if the data enters this range, the memory spikes and you get the error. (Watch the browser memory in Task Manager to see it spike). I'm using Firefox but it crashes in Chrome as well.

The following snippet will generate the attached wrong formatted bar chart. If more bars are used the formatting looks okay, so somehow the bar width and pos calculation for one or two datapoints is wrong.

func IssueChart() error {
    wuc := chart.BarChart{Title: "Weekly Data Usage"}
    wuc.XRange.Category = []string{"W1", "W2"}
    wuc.XRange.Label, wuc.YRange.Label = "Calendar Week", "Data Transfer (MB)"
    wuc.Key.Pos, wuc.Key.Cols, wuc.Key.Border = "otc", 2, -1
    wuc.YRange.ShowZero = true
    wuc.ShowVal = 0
    pos := []float64{0, 1}
    rx := []float64{100.0, 150.0}
    tx := []float64{50.0, 200.0}
    wuc.AddDataPair("RX (Download)", pos, rx,
        chart.Style{Symbol: 'o', LineColor: color.NRGBA{69, 117, 179, 0xff}, LineWidth: 2, FillColor: color.NRGBA{79, 127, 189, 0xff}})
    wuc.AddDataPair("TX (Upload)", pos, tx,
        chart.Style{Symbol: 'o', LineColor: color.NRGBA{182, 70, 67, 0xff}, LineWidth: 2, FillColor: color.NRGBA{192, 80, 77, 0xff}})
    // Save image
    igr := imgg.New(1024, 640, color.RGBA{0xff, 0xff, 0xff, 0xff}, nil, nil)
    wuc.Plot(igr)
    fh, err := os.Create("chart_issue.jpg")
    if err != nil {
        return err
    }
    err = jpeg.Encode(fh, igr.Image, nil)
    return err
}

Hello, I try to plot a bar chart with a logarithmic y axis, but I always get an out of memory exception in: chart.go:569 I tried hiding the tics, limiting the max range and setting delta to a tenth of my maximum value, but it's not helping. Do you have an idea how I can circumvent this? Interestingly, the example logarithmic chart works. I would be glad to provide further information if you require.

Greetings, Alex