resize

resize.go

This started out as a fork of the image resizing library for Go that used to be in Gorilla (I can't even find a link to the original code, it's that old) but seems to have been taken out.

It has since pretty much entirely been gutted and replaced.

Now, the main functionality that this library provides is a very opinionated view of image resizing and thumbnailing.

Specifically, it seems that every image resizing library out there expects you to tell it the width and height of the image that you are generating. That's fine except that in about two decades of web and application development, much of which has involved images, I've never encountered a situation where changing the aspect ratio of an image is desirable (not 100% true: sometimes if you're feeding things to a computer vision library, that's what you want, but never when generating images that humans will look at). Every image resizing use case I've encountered has been basically:

• make the image fit within a particular width or height while preserving the aspect ratio. Eg, scale it down so it's 100px tall.
• crop the image so it is a particular aspect ratio and then scale it to a particular size. 90% of the time this is a square.
• on very rare occasions, you need to scale the image to fit within a bounding box, while preserving the aspect ratio. Eg, fit it within a 100px wide by 200px box.

You just never need to change the aspect ratio, squishing and distorting the image. And yet, every image resizing API seems to lead you in that direction by default. Coaxing them to do the three use cases described above is almost always much more work than it ought to be.

So, that's what this library is for.

License remains BSD.

Installation

$ go get github.com/thraxil/resize

Quick Usage Example

package main
import (
    "os"
    "fmt"
    "image/jpeg"
    "log"
    "github.com/thraxil/resize"
)

func main() {
    file, err := os.Open("test.jpg")
    if err != nil {
        log.Fatal(err)
    }
    defer file.Close()
    
    // Decode the image.
    m, err := jpeg.Decode(file)
    if err != nil {
        fmt.Printf("error decoding image\n")
        log.Fatal(err)
	}
	outputImage := resize.Resize(m, "100s")
    outBounds := outputImage.Bounds()
    fmt.Printf("%q\n",outBounds)
    fl, err := os.OpenFile("out.jpg", os.O_CREATE|os.O_RDWR,0644)
    if err != nil {
        fmt.Println("couldn't write", err)
        return
    }
    defer fl.Close()
    jpeg.Encode(fl, outputImage, nil)
}