Golang - Getting the dimensions of an image. jpg, jpeg, png

images_dimensions.go

package main

import (
    "fmt"
    "image"
    "os"
    _ "image/jpeg"
    _ "image/png"
)

func main() {
    width, height := getImageDimension("rainy.jpg")
    fmt.Println("Width:", width, "Height:", height)
}

func getImageDimension(imagePath string) (int, int) {
    file, err := os.Open(imagePath)
    if err != nil {
        fmt.Fprintf(os.Stderr, "%v\n", err)
    }

    image, _, err := image.DecodeConfig(file)
    if err != nil {
        fmt.Fprintf(os.Stderr, "%s: %v\n", imagePath, err)
    }
    return image.Width, image.Height
}

I was just passing by and noticed this piece of code.

if err != nil {
    fmt.Fprintf(os.Stderr, "%v\n", err)
}

It can be written this way too.

if err != nil {
    log.Println(err)
}

Before

if err != nil {
    fmt.Fprintf(os.Stderr, "%s: %v\n", imagePath, err)
}

After

if err != nil {
    log.Println(imagePath, err)
}

The log package writes to stderr. Okay, bye. :)

Don't forget to close the file:
defer file.Close();

If you already have loaded an image with image.Decode(), you can also

b := img.Bounds()
imgWidth := b.Max.X
imgHeight := b.Max.Y

Thanks! I had never properly noticed the existence of func image.DecodeConfig before, which is great for me because I don't want to decode the whole image just to know its dimensions.

If you already have loaded an image with image.Decode(), you can also

b := img.Bounds()
imgWidth := b.Max.X
imgHeight := b.Max.Y

Great advice! Thanks

If you already have loaded an image with image.Decode(), you can also

b := img.Bounds()
imgWidth := b.Max.X
imgHeight := b.Max.Y

I needed something similar and this pointed me to a good direction. I used it like this though

b := img.Bounds()
width := b.Dx()
height := b.Dy()

img.Bounds() returns a Rectangle. Below is extract from the image package source code.

// A Rectangle contains the points with Min.X <= X < Max.X, Min.Y <= Y < Max.Y.
// It is well-formed if Min.X <= Max.X and likewise for Y. Points are always
// well-formed. A rectangle's methods always return well-formed outputs for
// well-formed inputs.
//
// A Rectangle is also an Image whose bounds are the rectangle itself. At
// returns color.Opaque for points in the rectangle and color.Transparent
// otherwise.
type Rectangle struct {
	Min, Max Point
}

// String returns a string representation of r like "(3,4)-(6,5)".
func (r Rectangle) String() string {
	return r.Min.String() + "-" + r.Max.String()
}

// Dx returns r's width.
func (r Rectangle) Dx() int {
	return r.Max.X - r.Min.X
}

// Dy returns r's height.
func (r Rectangle) Dy() int {
	return r.Max.Y - r.Min.Y
}

If you already have loaded an image with image.Decode(), you can also

b := img.Bounds()
imgWidth := b.Max.X
imgHeight := b.Max.Y

I needed something similar and this pointed me to a good direction. I used it like this though

b := img.Bounds()
width := b.Dx()
height := b.Dy()

img.Bounds() returns a Rectangle. Below is extract from the image package source code.

// A Rectangle contains the points with Min.X <= X < Max.X, Min.Y <= Y < Max.Y.
// It is well-formed if Min.X <= Max.X and likewise for Y. Points are always
// well-formed. A rectangle's methods always return well-formed outputs for
// well-formed inputs.
//
// A Rectangle is also an Image whose bounds are the rectangle itself. At
// returns color.Opaque for points in the rectangle and color.Transparent
// otherwise.
type Rectangle struct {
	Min, Max Point
}

// String returns a string representation of r like "(3,4)-(6,5)".
func (r Rectangle) String() string {
	return r.Min.String() + "-" + r.Max.String()
}

// Dx returns r's width.
func (r Rectangle) Dx() int {
	return r.Max.X - r.Min.X
}

// Dy returns r's height.
func (r Rectangle) Dy() int {
	return r.Max.Y - r.Min.Y
}

Thanks! found this very helpful for my case. :)

this also applies:

image..Bound().Dx - width
image..Bound().Dy - height