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
+12.5k Golang : Reverse IP address for reverse DNS lookup example
+10.4k Golang : Surveillance with web camera and OpenCV
+16.1k Golang : When to use init() function?
+5k Golang : Compound interest over time example
+6k Linux : How to fix Brother HL-1110 printing blank page problem
+13.9k Golang : Force download file example
+14.8k Golang : Delete files by extension
+8.6k Javascript : Read/parse JSON data from HTTP response
+6.8k Javascript : How to check a browser's Do Not Track status?
+7.7k Golang : Random integer with rand.Seed() within a given range
+12k Golang : Count number of runes in string
+24.4k Golang : How to write CSV data to file