How to reduce the image to go bringing it to a certain width and height?

I would take imagemagick - there is a binding to go https://github.com/gographics/imagick . And then - reading the documentation and studying the example - https://github.com/gographics/imagick/blob/master/examples/resize/main.go

But what width and height to set is already up to you.

Here is a library without binders: https://github.com/nfnt/resize

A simple example of use:

package main import ( "image/jpeg" "os" "github.com/nfnt/resize" ) func main(){ imgIn, _ := os.Open("test.jpg") imgJpg, _ := jpeg.Decode(imgIn) imgIn.Close() imgJpg = resize.Resize(600, 0, imgJpg, resize.Bicubic) // <-- Собственно изменение размера картинки imgOut, _ := os.Create("test-out.jpg") jpeg.Encode(imgOut, imgJpg,nil) imgOut.Close() } 

There is a golang.org/x/image/draw package that allows this.

When you resize an image, distortion and data loss occur. To achieve the desired effect, one or another interpolation method is used. Some methods give good performance - other quality. The above package has four interpolation methods built in:

• NearestNeighbor - nearest neighbor interpolation. The easiest and fastest algorithm. However, usually the result is poor quality. With the increase, the result becomes "square"
• ApproxBiLinear is a mix between NearestNeighbor and BiLinear. It is fast, but usually gives an average quality result
• BiLinear is slow, but gives good results.
• CatmullRom uses Catmull-Roma spline (English wiki ). Very slow, but gives a very good result.

CatmullRom Conversion Example

 import ( "image" "golang.org/x/image/draw" ) func main() { // открытие изображения источника // любым угодным способом src := openImage() // создаём пустое изображение для // записи необходимого размера dst := image.NewRGBA(image.Rect(0, 0, 200, 200)) // изменение размера draw.CatmullRom.Scale(dst, dst.Bounds(), src, src.Bounds(), draw.Over, nil) // готово // теперь dst содержит итоговое изображение } 

Image for example Result for different interpolation methods when halved

On dual-core Intel Core i3 M380 2.53GHz, the result of halving the time:

 | метод | время | |:---------------:|--------------:| | NearestNeighbor | 7.935489ms | | ApproxBiLinear | 14.876478ms | | BiLinear | 113.903067ms | | CatmullRom | 115.972061ms | 

A complete example of the application used can be found at gist.github.com . Using this example and various sets of source images, you can, after looking at the results, select the optimal interpolation method for your task.

• golang.org/x/image/draw
• sample application