golden/pdfxform a pdf rasterization server

go/pdf/pdf.go

Index: go/pdf/pdf.go
diff --git a/go/pdf/pdf.go b/go/pdf/pdf.go
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+/* PDF Rasterizer Package
+
+This package provides the Pdfium and Poppler rasterizers.  Pdfium
+requires the `pdfium_test` executable be located in the PATH.  Poppler
+requires `pdftoppm` (provided by poppler-utils) and `pnmtopng`
+(provided by netpbm). */
+
+package pdf
+
+type Rasterizer interface {
+	// Rasterize will take the path to a PDF file and rasterize the
+	// file.  If the file has multiple pages, discard all but the first
+	// page.  The output file will be in PNG format.
+	Rasterize(pdfInputPath, pngOutputPath string) error
+	// Return the name of this rasterizer.
+	String() string
+	// Return false if the rasterizer is found.
+	Enabled() bool
+}