Embed key-value data into png images.
go get github.com/sabhiram/png-embed
This library exposes two APIs:
package main
import (
"io/ioutil"
pngembed "github.com/sabhiram/png-embed"
)
func main() {
bs, _ := ioutil.ReadFile("sample.png")
// Encode the key "FOO" with the value "BAR" (string).
data, _ := pngembed.Embed(bs, "FOO", "BAR")
ioutil.WriteFile("sample.png", data, 755)
}EmbedFile is exactly like Embed but it accepts a path to a file instead of the PNG file data.
package main
import (
"io/ioutil"
pngembed "github.com/sabhiram/png-embed"
)
func main() {
// Encode the key "FOO" with the value "BAR" (string).
data, _ := pngembed.EmbedFile("sample.png", "FOO", "BAR")
ioutil.WriteFile("sample.png", data, 755)
}Since the Embed method accepts an interface and assumes that the interface adheres to JSON encoding, we can pass arbitrary structs or map[interface{}]interface{}s to it.
package main
import (
"io/ioutil"
pngembed "github.com/sabhiram/png-embed"
)
func main() {
s := struct {
Foo string `json:"Foo"`
Bar string `json:"Bar"`
}{
Foo: "FooValue",
Bar: "BarValue",
}
data, _ := pngembed.EmbedFile("sample.png", "FOO", s)
ioutil.WriteFile("sample.png", data, 755)
}TODO
There is a sample application in the example directory which takes a source image and attempts to encode data into it. You can run this using go run example/main.go with the following arguments:
-input string
input file name for the png [required]
-key string
key name for the data to inject [default="TEST_KEY"]
-value string
value for the data to inject [default="TEST_VALUE"]
-output string
output file name for the png [default="out.png"]
To inject in.png with the key value pair "fruit": "apple" and generate out.png:
$ go run example/main.go -input in.png -key fruit -value apple -output out.pngYou can then use something like pngcheck to verify that we did the right thing:
$ go run example/main.go -input ~/Desktop/test.png -key fruit -value apple -output out.png
$ pngcheck -t out.png
File: out.png (10785 bytes)
fruit:
apple
OK: out.png (225x225, 8-bit palette, non-interlaced, 78.7%).