add functions to export page or svg to pdf and png formats (zserge#22)

chrome.go

@@ -438,6 +438,61 @@ func (c *chrome) bounds() (Bounds, error) {
  return bounds.Bounds, err
 }
 
+func (c *chrome) pdf(width, height int) ([]byte, error) {
+ result, err := c.send("Page.printToPDF", h{
+ "paperWidth": float32(width) / 96,
+ "paperHeight": float32(height) / 96,
+ })
+ if err != nil {
+ return nil, err
+ }
+ pdf := struct {
+ Data []byte `json:"data"`
+ }{}
+ err = json.Unmarshal(result, &pdf)
+ return pdf.Data, err
+}
+
+func (c *chrome) png(x, y, width, height int, bg uint32, scale float32) ([]byte, error) {
+ if x == 0 && y == 0 && width == 0 && height == 0 {
+ // By default either use SVG size if it's an SVG, or use A4 page size
+ bounds, err := c.eval(`document.rootElement ? [document.rootElement.x.baseVal.value, document.rootElement.y.baseVal.value, document.rootElement.width.baseVal.value, document.rootElement.height.baseVal.value] : [0,0,816,1056]`)
+ if err != nil {
+ return nil, err
+ }
+ rect := make([]int, 4)
+ if err := json.Unmarshal(bounds, &rect); err != nil {
+ return nil, err
+ }
+ x, y, width, height = rect[0], rect[1], rect[2], rect[3]
+ }
+
+ _, err := c.send("Emulation.setDefaultBackgroundColorOverride", h{
+ "color": h{
+ "r": (bg >> 16) & 0xff,
+ "g": (bg >> 8) & 0xff,
+ "b": bg & 0xff,
+ "a": (bg >> 24) & 0xff,
+ },
+ })
+ if err != nil {
+ return nil, err
+ }
+ result, err := c.send("Page.captureScreenshot", h{
+ "clip": h{
+ "x": x, "y": y, "width": width, "height": height, "scale": scale,
+ },
+ })
+ if err != nil {
+ return nil, err
+ }
+ pdf := struct {
+ Data []byte `json:"data"`
+ }{}
+ err = json.Unmarshal(result, &pdf)
+ return pdf.Data, err
+}
+
 func (c *chrome) kill() error {
  if c.ws != nil {
  if err := c.ws.Close(); err != nil {

export.go

@@ -0,0 +1,56 @@
+package lorca
+
+import (
+ "fmt"
+ "io/ioutil"
+ "os"
+)
+
+const (
+ // PageA4Width is a width of an A4 page in pixels at 96dpi
+ PageA4Width = 816
+ // PageA4Height is a height of an A4 page in pixels at 96dpi
+ PageA4Height = 1056
+)
+
+// PDF converts a given URL (may be a local file) to a PDF file. Script is
+// evaluated before the page is printed to PDF, you may modify the contents of
+// the page there of wait until the page is fully rendered. Width and height
+// are page bounds in pixels. PDF by default uses 96dpi density. For A4 page
+// you may use PageA4Width and PageA4Height constants.
+func PDF(url, script string, width, height int) ([]byte, error) {
+ return doHeadless(url, func(c *chrome) ([]byte, error) {
+ c.eval(script)
+ return c.pdf(width, height)
+ })
+}
+
+// PNG converts a given URL (may be a local file) to a PNG image. Script is
+// evaluated before the "screenshot" is taken, so you can modify the contents
+// of a URL there. Image bounds are provides in pixels. Background is in ARGB
+// format, the default value of zero keeps the background transparent. Scale
+// allows zooming the page in and out.
+//
+// This function is most convenient to convert SVG to PNG of different sizes,
+// for example when preparing Lorca app icons.
+func PNG(url, script string, x, y, width, height int, bg uint32, scale float32) ([]byte, error) {
+ return doHeadless(url, func(c *chrome) ([]byte, error) {
+ c.eval(script)
+ return c.png(x, y, width, height, bg, scale)
+ })
+}
+
+func doHeadless(url string, f func(c *chrome) ([]byte, error)) ([]byte, error) {
+ dir, err := ioutil.TempDir("", "lorca")
+ if err != nil {
+ return nil, err
+ }
+ defer os.RemoveAll(dir)
+ args := append(defaultChromeArgs, fmt.Sprintf("--user-data-dir=%s", dir), "--remote-debugging-port=0", "--headless", url)
+ chrome, err := newChromeWithArgs(ChromeExecutable(), args...)
+ if err != nil {
+ return nil, err
+ }
+ defer chrome.kill()
+ return f(chrome)
+}