Golang : Get RGBA values of each image pixel
Problem :
You need to find out each pixels R,G,B,A values on an image. Maybe to do ASCII art, edge detection algorithm for cognitive purpose or some advanced image processing. How to do that?
Solution :
Get the width and height of an image file with image.DecodeConfig()
function and then iterate each pixel base on width/height on the image covering entire image. At each pixel, use image.At()
function's RGBA() method to retrieve the R,G,B,A values.
For example :
package main
import (
"fmt"
"image"
"image/jpeg"
"os"
)
func init() {
// damn important or else At(), Bounds() functions will
// caused memory pointer error!!
image.RegisterFormat("jpeg", "jpeg", jpeg.Decode, jpeg.DecodeConfig)
}
func main() {
imgfile, err := os.Open("./img.jpg")
if err != nil {
fmt.Println("img.jpg file not found!")
os.Exit(1)
}
defer imgfile.Close()
// get image height and width with image/jpeg
// change accordinly if file is png or gif
imgCfg, _, err := image.DecodeConfig(imgfile)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
width := imgCfg.Width
height := imgCfg.Height
fmt.Println("Width : ", width)
fmt.Println("Height : ", height)
// we need to reset the io.Reader again for image.Decode() function below to work
// otherwise we will - panic: runtime error: invalid memory address or nil pointer dereference
// there is no build in rewind for io.Reader, use Seek(0,0)
imgfile.Seek(0, 0)
// get the image
img, _, err := image.Decode(imgfile)
fmt.Println(img.At(10, 10).RGBA())
for y := 0; y < height; y++ {
for x := 0; x < width; x++ {
r, g, b, a := img.At(x, y).RGBA()
fmt.Printf("[X : %d Y : %v] R : %v, G : %v, B : %v, A : %v \n", x, y, r, g, b, a)
}
}
}
By Adam Ng
IF you gain some knowledge or the information here solved your programming problem. Please consider donating to the less fortunate or some charities that you like. Apart from donation, planting trees, volunteering or reducing your carbon footprint will be great too.
Advertisement
Tutorials
+27k Golang : Convert file content into array of bytes
+19.4k Golang : Check if directory exist and create if does not exist
+13.3k Golang : Convert(cast) int to int64
+23k Golang : Gorilla mux routing example
+25.8k Golang : convert rune to integer value
+11.4k Golang : How to pipe input data to executing child process?
+9.7k Android Studio : Indicate progression with ProgressBar example
+17.5k Golang : Check if IP address is version 4 or 6
+6.3k Golang : Get missing location after unmarshal binary and gob decode time.
+9.7k Golang : How to extract video or image files from html source code
+28.1k Golang : Decode/unmarshal unknown JSON data type with map[string]interface
+14.3k Golang : Check if a file exist or not