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rgbe

Description

rgbe is a simple RGBE encoding/decoding library for Go. The RGBE format was invented by Greg Ward for compact storage of HDR images. This library is based on code written by Bruce Walter.

Reading of both the RLE-compressed and uncompressed variants is supported. Images are always written with RLE-comression. No additional header information (e.g. gamma and exposure) are read or written.

Pixel data is stored in RGB order in a []float32 slice, starting in the left top corner and going downards from left to right.

Example

This example reads a RGBE encoded image from disk, computes the average luminance and stores a black and white variant of the image in RGBE format on disk again. Error handling is ommitted for brevity.

package main

import (
	"github.com/Opioid/rgbe"
	"os"
	"fmt"
)

func main() {
	fi, _ := os.Open("output.hdr")
	defer fi.Close()

	width, height, data, _ := rgbe.Decode(fi)

	total := float32(width * height)
	averageLuminance := float32(0)

	for y := 0; y < height; y++ {
		for x := 0; x < width; x++ {
			o := (width * y + x) * 3
			r, g, b := data[o], data[o + 1], data[o + 2]
			l := luminance(r, g, b)
			averageLuminance += l / total
			data[o], data[o + 1], data[o + 2] = l, l, l
		}
	}

	fmt.Printf(
		"RGBE image %d x %d size, average luminance is %v\n", 
		width, height, averageLuminance)

	fo, _ := os.Create("bw.hdr")
	defer fo.Close()

	rgbe.Encode(fo, width, height, data)
}

func luminance(r, g, b float32) float32 {
	return r * 0.299 + g * 0.587 + b * 0.114
}

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