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main.go
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main.go
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package main
import (
"fmt"
"image"
"image/color"
"image/jpeg"
"image/png"
"io/ioutil"
"log"
"math"
"os"
)
var fileName = "image.png"
type Pixel struct {
R, G, B, A int
}
func main() {
if len(os.Args) < 3 || (os.Args[1] != "-w" && os.Args[1] != "-r" && os.Args[1] != "-f") || (os.Args[1] == "-w" && len(os.Args) != 4) || (os.Args[1] == "-f" && len(os.Args) != 4) {
fmt.Println("Invalid Usage")
fmt.Println("Usage: go run main.go -w fileName \"message here\" ")
fmt.Println("Usage: go run main.go -f fileName \"file name\" ")
fmt.Println("Usage: go run main.go -r fileName ")
os.Exit(1)
}
mode := os.Args[1]
fileName = os.Args[2]
if _, err := os.Stat(fileName); os.IsNotExist(err) {
fmt.Println("Image file doesn't exist")
os.Exit(1)
}
if mode == "-w" {
write(os.Args[3])
} else if mode == "-r" {
read()
} else if mode == "-f" {
f, err := ioutil.ReadFile(os.Args[3])
if err != nil {
fmt.Println("Input text file doesn't exist")
log.Fatal(err)
}
write(string(f))
}
}
func write(input string) {
// TESTING STRING TO BINARY
newString := convertString(input)
bitLength := i2b(len(newString), 32)
// Load fileName and create a placeholder with same dimensions
pixelArray, width, height := getImage()
if (height * width * 3) < (len(newString)*8)+11 {
log.Fatal("Message is too long for given image file.\nTry with a bigger image.")
}
img := image.NewNRGBA(image.Rect(0, 0, width, height))
// Write the length of the message
writeBits(0, pixelArray, bitLength)
writeBits(11, pixelArray, newString)
fmt.Printf("Length of message: %d characters\n", len(input))
fmt.Println("Number of pixels being used to write message: ", int(math.Ceil((float64(len(newString)) / 3))))
// Copying pixelArray to placeholder
for y := 0; y < height; y++ {
for x := 0; x < width; x++ {
img.Set(x, y, color.NRGBA{
R: uint8(pixelArray[(y*width)+(x)].R),
G: uint8(pixelArray[(y*width)+(x)].G),
B: uint8(pixelArray[(y*width)+(x)].B),
A: 255,
})
}
}
fmt.Println("Writing to file...")
// Writing the placeholder to a png file
output := fileName[:len(fileName)-3] + "png"
f, err := os.Create(output)
if err != nil {
log.Fatal(err)
}
if err := png.Encode(f, img); err != nil {
f.Close()
log.Fatal(err)
}
fmt.Println("Done writing to file")
}
func writeBits(offset int, pixelArray []Pixel, source []byte) []Pixel {
// Takes input (source) and writes to pixelArray starting at a given offset
numPix := int(math.Ceil(float64(len(source)) / 3))
arrayLen := len(pixelArray)
sourceLen := len(source)
for i := 0; i < numPix; i++ {
position := arrayLen - 1 - offset - i
if int(source[i*3]) == 1 {
pixelArray[position].R = pixelArray[position].R | int(source[i*3])
} else {
pixelArray[position].R = pixelArray[position].R & 254
}
if (i*3)+1 >= sourceLen {
break
}
if int(source[(i*3)+1]) == 1 {
pixelArray[position].G = pixelArray[position].G | int(source[(i*3)+1])
} else {
pixelArray[position].G = pixelArray[position].G & 254
}
if (i*3)+2 >= sourceLen {
break
}
if int(source[(i*3)+2]) == 1 {
pixelArray[position].B = pixelArray[position].B | int(source[(i*3)+2])
} else {
pixelArray[position].B = pixelArray[position].B & 254
}
}
return pixelArray
}
func read() {
// Open the file and get the pixel array
pixelArray, _, _ := getImage()
// Getting stored message length, including extra unused bit
var leng []byte
for i := range pixelArray[len(pixelArray)-11:] {
leng = append(leng, byte(pixelArray[len(pixelArray)-i-1].R&1))
leng = append(leng, byte(pixelArray[len(pixelArray)-i-1].G&1))
leng = append(leng, byte(pixelArray[len(pixelArray)-i-1].B&1))
}
// Convert from binary to decimal
messageLength := b2d(leng[:len(leng)-1])
// Retreive the message pixels
var tmpMessage []byte
for i := range pixelArray[(len(pixelArray) - (11 + int(math.Ceil(messageLength/3)))) : len(pixelArray)-11] {
tmpMessage = append(tmpMessage, byte(pixelArray[len(pixelArray)-i-12].R&1))
tmpMessage = append(tmpMessage, byte(pixelArray[len(pixelArray)-i-12].G&1))
tmpMessage = append(tmpMessage, byte(pixelArray[len(pixelArray)-i-12].B&1))
}
// Retreive their bits
var message []byte
for i := 0; i < int(messageLength/8); i++ {
var char byte = 0
for j := 0; j < 8; j++ {
char = (char << 1) + tmpMessage[(i*8)+j]
}
message = append(message, char)
}
fmt.Printf("Message size: %d characters\n", len(message))
fmt.Println("Message:\n", string(message))
}
func getImage() ([]Pixel, int, int) {
// Opens the image and return its pixels and dimensions
file, err := os.Open(fileName)
if err != nil {
log.Fatal(err)
}
defer file.Close()
fileType := fileName[len(fileName)-3:] // Get the file extension
var loadedImage image.Image
if fileType == "jpg" { // Input is a jpg
loadedImage, err = jpeg.Decode(file)
if err != nil {
log.Fatal(err)
}
} else if fileType == "png" { // Input is a png
loadedImage, _, err = image.Decode(file)
if err != nil {
log.Fatal(err)
}
} else {
log.Fatal("Unsuported image file type")
}
height := loadedImage.Bounds().Dy()
width := loadedImage.Bounds().Dx()
var pixels []Pixel
// Gather all the pixels
for y := 0; y < height; y++ {
for x := 0; x < width; x++ {
pixels = append(pixels, toPixel(loadedImage.At(x, y).RGBA()))
}
}
return pixels, width, height
}
func toPixel(r uint32, g uint32, b uint32, a uint32) Pixel {
// Takes in a golang pixel in rgba format and converts all the values from uint32s to normal integers
return Pixel{int(r / 257), int(g / 257), int(b / 257), int(a / 257)}
}
func b2d(input []byte) float64 {
// Takes in a binary representation and returns a decimal equivalent
result := 0.0
for i, val := range input {
power := len(input) - 1 - i
if val == 1 {
result += math.Pow(2, float64(power))
}
}
return result
}
func i2b(input int, numBytes int) []byte {
// Converts an integer to binary
var result []byte
for i := 0; i < numBytes; i++ {
result = append(result, 0)
}
for i := 0; i < numBytes; i++ {
if (input & 1) == 1 {
result[numBytes-1-i] = 1
}
input = input >> 1
}
return result
}
func convertString(input string) []byte {
var temp []byte
for _, char := range input {
for _, bytes := range i2b(int(char), 8) {
// Convert each character's ord value to bits
temp = append(temp, bytes)
}
}
// fmt.Println(temp)
return temp
}