// Encode image.Image with Mapniks image encoder.
func Encode(img image.Image, format string) ([]byte, error) {
var i *C.mapnik_image_t
switch img := img.(type) {
// XXX does mapnik expect NRGBA or RGBA? this might stop working
//as expected if we start encoding images with full alpha channel
case *image.NRGBA:
i = C.mapnik_image_from_raw(
(*C.uint8_t)(unsafe.Pointer(&img.Pix[0])),
C.int(img.Bounds().Dx()),
C.int(img.Bounds().Dy()),
)
case *image.RGBA:
i = C.mapnik_image_from_raw(
(*C.uint8_t)(unsafe.Pointer(&img.Pix[0])),
C.int(img.Bounds().Dx()),
C.int(img.Bounds().Dy()),
)
}
if i == nil {
return nil, errors.New("unable to create image from raw")
}
defer C.mapnik_image_free(i)
cformat := C.CString(format)
b := C.mapnik_image_to_blob(i, cformat)
if b == nil {
return nil, errors.New("mapnik: " + C.GoString(C.mapnik_image_last_error(i)))
}
C.free(unsafe.Pointer(cformat))
defer C.mapnik_image_blob_free(b)
return C.GoBytes(unsafe.Pointer(b.ptr), C.int(b.len)), nil
}
// Render returns the map as an encoded image.
func (m *Map) Render(opts RenderOpts) ([]byte, error) {
scaleFactor := opts.ScaleFactor
if scaleFactor == 0.0 {
scaleFactor = 1.0
}
i := C.mapnik_map_render_to_image(m.m, C.double(opts.Scale), C.double(scaleFactor))
if i == nil {
return nil, m.lastError()
}
defer C.mapnik_image_free(i)
if opts.Format == "raw" {
size := 0
raw := C.mapnik_image_to_raw(i, (*C.size_t)(unsafe.Pointer(&size)))
return C.GoBytes(unsafe.Pointer(raw), C.int(size)), nil
}
var format *C.char
if opts.Format != "" {
format = C.CString(opts.Format)
} else {
format = C.CString("png256")
}
b := C.mapnik_image_to_blob(i, format)
if b == nil {
return nil, errors.New("mapnik: " + C.GoString(C.mapnik_image_last_error(i)))
}
C.free(unsafe.Pointer(format))
defer C.mapnik_image_blob_free(b)
return C.GoBytes(unsafe.Pointer(b.ptr), C.int(b.len)), nil
}