ekuiper-new/extensions/functions/image/thumbnail.go

// Copyright 2021 EMQ Technologies Co., Ltd.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package main

import (
	"bytes"
	"fmt"
	"image"
	"image/jpeg"
	"image/png"

	"github.com/nfnt/resize"

	"github.com/lf-edge/ekuiper/pkg/api"
)

type thumbnail struct{}

func (f *thumbnail) Validate(args []interface{}) error {
	if len(args) != 3 {
		return fmt.Errorf("The thumbnail function supports 3 parameters, but got %d", len(args))
	}
	return nil
}

func (f *thumbnail) Exec(args []interface{}, _ api.FunctionContext) (interface{}, bool) {
	arg, ok := args[0].([]byte)
	if !ok {
		return fmt.Errorf("arg[0] is not a bytea, got %v", args[0]), false
	}
	maxWidth, ok := args[1].(int)
	if !ok || 0 > maxWidth {
		return fmt.Errorf("arg[1] is not a bigint, got %v", args[1]), false
	}
	maxHeight, ok := args[2].(int)
	if !ok || 0 > maxHeight {
		return fmt.Errorf("arg[2] is not a bigint, got %v", args[2]), false
	}
	img, format, err := image.Decode(bytes.NewReader(arg))
	if nil != err {
		return fmt.Errorf("image decode error:%v", err), false
	}
	img = resize.Thumbnail(uint(maxWidth), uint(maxHeight), img, resize.Bilinear)

	var b []byte
	buf := bytes.NewBuffer(b)
	switch format {
	case "png":
		err = png.Encode(buf, img)
	case "jpeg":
		err = jpeg.Encode(buf, img, nil)
	default:
		return fmt.Errorf("%s image type is not currently supported", format), false
	}
	if nil != err {
		return fmt.Errorf("image encode error:%v", err), false
	}
	return buf.Bytes(), true
}

func (f *thumbnail) IsAggregate() bool {
	return false
}