Golang : How to read JPG(JPEG), GIF and PNG files ?
Was having a hard time trying to figure out why all my attempts to open and read JPG or JPEG format image files will cause memory pointer error(when trying to get At() and Bounds() functions to work).
Apparently, in Golang, one must register the format in the init() section first before attempting to open/read image files and perform operation on the files.
The code below is a simple guide on how to open and read JPEG/JPG format image files :
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()
img, _, err := image.Decode(imgfile)
fmt.Println(img.At(10, 10))
bounds := img.Bounds()
fmt.Println(bounds)
canvas := image.NewAlpha(bounds)
// is this image opaque
op := canvas.Opaque()
fmt.Println(op)
}
Sample output :
{255 128 128}
(0,0)-(760,479)
false
This should apply to the PNG and GIF encoded images as well. ( see https://www.socketloop.com/references/golang-image-registerformat-function-example )
See also : Golang : Save image to PNG, JPEG or GIF format.
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
+17k Golang : Archive directory with tar and gzip
+8.4k Golang : Fix - does not implement sort.Interface (missing Len method)
+12.1k Golang : Get current time
+5.3k Mac OSX : Find large files by size
+8.5k Golang : ISO8601 Duration Parser example
+4.6k Javascript : Generate random key with specific length
+7.2k Golang : How to check if a website is served via HTTPS
+18.4k Golang : Read a file into an array or slice example
+4.7k Golang : Find the longest line of text example
+6.8k Golang : On lambda, anonymous, inline functions and function literals
+11.7k Golang : Google Drive API upload and rename example
+6.2k Golang : Get final or effective URL with Request.URL example