images

README

Images

The images package provides methods for working with images.

ImageCropper

ImageCropper is a service designed to crop images. There are a couple of ways to perform a crop. The first is a traditional crop starting from the top left corner with a width and height (pixels or ratio). The second is a crop originating from the center, going out a number of pixels or ratio.

Here is an example of cropping from the top left.

package main

import (
	"bytes"
	"image"
	"io/ioutil"
	"os"

	"github.com/ResurgenceIT/kit/v6/images"
)

func main() {
	var (
		err          error
		imageBytes   []byte
		croppedBytes *bytes.Buffer
		newFile      *os.File
	)

	/*
	 * Open the original image
	 */
	if imageBytes, err = ioutil.ReadFile("./yolie.jpeg"); err != nil {
		panic(err)
	}

	cropper := images.ImageCropper{}

	croppedBytes, err = cropper.Crop(imageBytes, images.CropOptions{
		Anchor:     image.Point{X: 10, Y: 10},
		AnchorMode: images.CropAnchorModeTopLeft,
		Height:     100,
		UseRatio:   false,
		Width:      100,
	})

	if err != nil {
		panic(err)
	}

	if newFile, err = os.Create("./new-image.jpg"); err != nil {
		panic(err)
	}

	if _, err = croppedBytes.WriteTo(newFile); err != nil {
		panic(err)
	}

	newFile.Close()
}

Now here is an example of a center crop with a 1:1 ratio (square).

package main

import (
	"bytes"
	"io/ioutil"
	"os"

	"github.com/ResurgenceIT/kit/v6/images"
)

func main() {
	var (
		err          error
		imageBytes   []byte
		croppedBytes *bytes.Buffer
		newFile      *os.File
	)

	/*
	 * Open the original image
	 */
	if imageBytes, err = ioutil.ReadFile("./image.jpeg"); err != nil {
		panic(err)
	}

	cropper := images.ImageCropper{}

	croppedBytes, err = cropper.Crop(imageBytes, images.CropOptions{
		AnchorMode: images.CropAnchorModeCentered,
		Height:     3,
		UseRatio:   true,
		Width:      4,
	})

	if err != nil {
		panic(err)
	}

	if newFile, err = os.Create("./new-image.png"); err != nil {
		panic(err)
	}

	if _, err = croppedBytes.WriteTo(newFile); err != nil {
		panic(err)
	}

	newFile.Close()
}

Resizer

The resizer service provides methods for resizing images.

ResizeImage

ResizeImage takes a source image, and a predefined image size, then returns the proportionally resized image. Sizes are:

• Thumbnail - Resizes the image to a 10th of its original size
• Small - Resizes the image to 25% of its original size
• Medium - Resizes the image to 50% of its original size
• Large - Original size

Below is an example of opening an image file and resizing it, saving it as a new file.

package main

import (
	"bytes"
	"os"

	"github.com/ResurgenceIT/kit/v6/images"
)

func main() {
	var (
		err          error
		originalFile *os.File
		newFile      *os.File
		resizedBytes *bytes.Buffer
	)

	/*
	 * Open the original image
	 */
	if originalFile, err = os.Open("./image.jpeg"); err != nil {
		panic(err)
	}

	defer originalFile.Close()

	resizer := images.Resizer{}

	if resizedBytes, err = resizer.ResizeImage(originalFile, "image/jpeg", images.MEDIUM); err != nil {
		panic(err)
	}

	if newFile, err = os.Create("./new-image.jpg"); err != nil {
		panic(err)
	}

	if _, err = resizedBytes.WriteTo(newFile); err != nil {
		panic(err)
	}

	newFile.Close()
}

ResizeImagePixels

ResizeImagePixels is similar to ResizeImage, except it deals with a specific width and height setting instead of relative sizing. Note that this method does not concern itself with preserving aspect ratio.

package main

import (
	"bytes"
	"os"

	"github.com/ResurgenceIT/kit/v6/images"
)

func main() {
	var (
		err          error
		originalFile *os.File
		newFile      *os.File
		resizedBytes *bytes.Buffer
	)

	/*
	 * Open the original image
	 */
	if originalFile, err = os.Open("./image.jpeg"); err != nil {
		panic(err)
	}

	defer originalFile.Close()

	resizer := images.Resizer{}

	if resizedBytes, err = resizer.ResizeImagePixels(originalFile, "image/jpeg", 200, 200); err != nil {
		panic(err)
	}

	if newFile, err = os.Create("./new-image.jpg"); err != nil {
		panic(err)
	}

	if _, err = resizedBytes.WriteTo(newFile); err != nil {
		panic(err)
	}

	newFile.Close()
}

Documentation

Index

• Variables
• type CropAnchorMode
• type CropOptions
  • func NewCropOptions() *CropOptions
• type IImageCropper
• type IResizer
• type ImageCropper
  • func (ic ImageCropper) Crop(imageBytes []byte, cropOptions CropOptions) (*bytes.Buffer, error)
• type ImageSize
  • func (is ImageSize) String() string
• type MockResizer
  • func (m MockResizer) ResizeImage(source io.ReadSeeker, contentType string, imageSize ImageSize) (*bytes.Buffer, error)
  • func (m MockResizer) ResizeImagePixels(source io.ReadSeeker, contentType string, width, height int) (*bytes.Buffer, error)
• type Resizer
  • func (r Resizer) ResizeImage(source io.ReadSeeker, contentType string, imageSize ImageSize) (*bytes.Buffer, error)
  • func (r Resizer) ResizeImagePixels(source io.ReadSeeker, contentType string, width, height int) (*bytes.Buffer, error)

Variables

var ErrImageFormatNotFound = fmt.Errorf("Image format not found")

ErrImageFormatNotFound is used when the provided image format is unsupported

var ErrInvalidFileType = errors.New("Invalid image type. Supported image formats are JPG and PNG")

ErrInvalidFileType is an error when the user uploads a bad file type

Types

type CropAnchorMode

type CropAnchorMode string

CropAnchorMode is used to describe from where a crop happens

var CropAnchorModeCentered CropAnchorMode = "centered"

CropAnchorModeCentered crops from the center

var CropAnchorModeTopLeft CropAnchorMode = "top-left"

CropAnchorModeTopLeft crops from top-left

type CropOptions

type CropOptions struct {
	Anchor     image.Point
	AnchorMode CropAnchorMode
	Height     int
	UseRatio   bool
	Width      int
}

CropOptions describes how an image is cropped. Width/Height defines how big to make the image. AnchorMode describes how to apply the crop anchor point. Valid options are top-left, centered. Anchor describes the X/Y offset from top left if the anchor mode is top-left. UseRatio, when true, makes width/height a ratio-based instead of pixels.

func NewCropOptions

func NewCropOptions() *CropOptions

NewCropOptions creates a new structure with default values filled in

type IImageCropper

type IImageCropper interface {
	Crop(imageBytes []byte, cropOptions CropOptions) (*bytes.Buffer, error)
}

IImageCropper is an interface for cropping images

type IResizer

type IResizer interface {
	ResizeImage(source io.ReadSeeker, contentType string, imageSize ImageSize) (*bytes.Buffer, error)
	ResizeImagePixels(source io.ReadSeeker, contentType string, width, height int) (*bytes.Buffer, error)
}

IResizer is an interface to describe structs that resize images

type ImageCropper

type ImageCropper struct{}

ImageCropper crops images

func (ImageCropper) Crop

func (ic ImageCropper) Crop(imageBytes []byte, cropOptions CropOptions) (*bytes.Buffer, error)

Crop takes an image reader and performs a crop based on the options provided. It returns the newly cropped image in the form of a PNG

type ImageSize

type ImageSize string

ImageSize describes generic image sizes

const (
	DEFAULT   ImageSize = "default"
	THUMBNAIL ImageSize = "thumbnail"
	SMALL     ImageSize = "small"
	MEDIUM    ImageSize = "medium"
	LARGE     ImageSize = "large"
)

func (ImageSize) String

func (is ImageSize) String() string

type MockResizer

type MockResizer struct {
	ResizeImageFunc       func(source io.ReadSeeker, contentType string, imageSize ImageSize) (*bytes.Buffer, error)
	ResizeImagePixelsFunc func(source io.ReadSeeker, contentType string, width, height int) (*bytes.Buffer, error)
}

func (MockResizer) ResizeImage

func (m MockResizer) ResizeImage(source io.ReadSeeker, contentType string, imageSize ImageSize) (*bytes.Buffer, error)

func (MockResizer) ResizeImagePixels

func (m MockResizer) ResizeImagePixels(source io.ReadSeeker, contentType string, width, height int) (*bytes.Buffer, error)

type Resizer

type Resizer struct{}

A Resizer contains methods for resizing images and re-encoding them.

func (Resizer) ResizeImage

func (r Resizer) ResizeImage(source io.ReadSeeker, contentType string, imageSize ImageSize) (*bytes.Buffer, error)

ResizeImage takes a source image, content type (MIME), and a image size ( THUMBNAIL, SMALL, MEDIUM, LARGE) and resizes proportionally.

func (Resizer) ResizeImagePixels

func (r Resizer) ResizeImagePixels(source io.ReadSeeker, contentType string, width, height int) (*bytes.Buffer, error)

ResizeImagePixels resizes a source image to the specified widthxheight.