[FIXED] Why I'm getting segmentation violation error in Go

Issue

I'm trying to import 2 png image and paste one on top of the other. The output will be jpeg.

When ever I run the code below, I got this error:

image: unknown format
image: unknown format
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x109d7a4]
goroutine 1 [running]:
main.main()

Error is coming whenever I use "Bounds()" method. What do you think is the cause.

code:

func main() {
    imgFile1, err := os.Open("./pics/00/body.png")
    if err != nil {
        fmt.Println(err)
    }
    defer imgFile1.Close()
    imgFile2, err := os.Open("./pics/01/face.png")
    if err != nil {
        fmt.Println(err)
    }
    defer imgFile2.Close()
    img1, _, err := image.Decode(imgFile1)
    if err != nil {
        fmt.Println(err)
    }
    img2, _, err := image.Decode(imgFile2)
    if err != nil {
        fmt.Println(err)
    }
    //new rectangle for the second image
    sp1 := image.Point{0,0}
    sp2 := image.Point{img1.Bounds().Dx(),img1.Bounds().Dy()}
    r2 := image.Rectangle{sp1, sp2}

    //create new image
    rgba := image.NewRGBA(r2)

    //draw the two images into this new image
    draw.Draw(rgba, r2, img1, image.Point{0, 0}, draw.Src)
    draw.Draw(rgba, r2, img2, image.Point{0, 0}, draw.Src)

    //export it
    out, err := os.Create("./output.jpg")
    if err != nil {
        fmt.Println(err)
    }
    defer out.Close()

    var opt jpeg.Options
    opt.Quality = 80

    jpeg.Encode(out, rgba, &opt)
}

Solution

I'm not sure why Go has two ways to decode like this. If you know the file type, I think it's better to just use the specific package:

package main

import (
   "fmt"
   "image/png"
   "net/http"
)

const ava = "http://gravatar.com/avatar/5ec9c21c8d54825b04def7a41998d18d"

func main() {
   r, err := http.Get(ava)
   if err != nil {
      panic(err)
   }
   defer r.Body.Close()
   i, err := png.Decode(r.Body)
   if err != nil {
      panic(err)
   }
   dx := i.Bounds().Dx()
   fmt.Println(dx)
}

If you insist on using the other method, you will need to add an import (thanks to mkopriva):

import (
   "image"
   _ "image/png"
)

https://godocs.io/image/png#Decode

Answered By - Zombo

Answer Checked By - Katrina (PHPFixing Volunteer)