// Copyright 2012 The Go Authors. All rights reserved.// Use of this source code is governed by a BSD-style// license that can be found in the LICENSE file. // This example demonstrates decoding a JPEG image and examining its pixels.package image_test import (	"encoding/base64"	"fmt"	"image"	"log"	"strings" 	// Package image/jpeg is not used explicitly in the code below,	// but is imported for its initialization side-effect, which allows	// image.Decode to understand JPEG formatted images. Uncomment these	// two lines to also understand GIF and PNG images:	// _ "image/gif"	// _ "image/png"	_ "image/jpeg") func Example() {	// Decode the JPEG data. If reading from file, create a reader with	//	// reader, err := os.Open("testdata/video-001.q50.420.jpeg")	// if err != nil {	//     log.Fatal(err)	// }	// defer reader.Close()	reader := base64.NewDecoder(base64.StdEncoding, strings.NewReader(data))	m, _, err := image.Decode(reader)	if err != nil {		log.Fatal(err)	}	bounds := m.Bounds() 	// Calculate a 16-bin histogram for m's red, green, blue and alpha components.	//	// An image's bounds do not necessarily start at (0, 0), so the two loops start	// at bounds.Min.Y and bounds.Min.X. Looping over Y first and X second is more	// likely to result in better memory access patterns than X first and Y second.	var histogram [16][4]int	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {		for x := bounds.Min.X; x < bounds.Max.X; x++ {			r, g, b, a := m.At(x, y).RGBA()			// A color's RGBA method returns values in the range [0, 65535].			// Shifting by 12 reduces this to the range [0, 15].			histogram[r>>12][0]++			histogram[g>>12][1]++			histogram[b>>12][2]++			histogram[a>>12][3]++		}	} 	// Print the results.	fmt.Printf("%-14s %6s %6s %6s %6s\n", "bin", "red", "green", "blue", "alpha")	for i, x := range histogram {		fmt.Printf("0x%04x-0x%04x: %6d %6d %6d %6d\n", i<<12, (i+1)<<12-1, x[0], x[1], x[2], x[3])	}	// Output:	// bin               red  green   blue  alpha	// 0x0000-0x0fff:    364    790   7242      0	// 0x1000-0x1fff:    645   2967   1039      0	// 0x2000-0x2fff:   1072   2299    979      0	// 0x3000-0x3fff:    820   2266    980      0	// 0x4000-0x4fff:    537   1305    541      0	// 0x5000-0x5fff:    319    962    261      0	// 0x6000-0x6fff:    322    375    177      0	// 0x7000-0x7fff:    601    279    214      0	// 0x8000-0x8fff:   3478    227    273      0	// 0x9000-0x9fff:   2260    234    329      0	// 0xa000-0xafff:    921    282    373      0	// 0xb000-0xbfff:    321    335    397      0	// 0xc000-0xcfff:    229    388    298      0	// 0xd000-0xdfff:    260    414    277      0	// 0xe000-0xefff:    516    428    298      0	// 0xf000-0xffff:   2785   1899   1772  15450} const data = 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