How to Extract a Pixel Array from an Image in Go for `texImage2D`?

Retrieving a Pixel Array from an Image in Go

Problem:

Extracting a pixel array from an image in the form of a byte array is necessary for passing it to the texImage2D method of gl.Context. The desired pixel array consists of RGBA values arranged in a sequential order from left to right and top to bottom.

Solution:

To obtain the pixel array, the following steps can be taken:

1. Obtain the Image:
   Load the image using image.Decode(a) from an io.Reader like os.File or http.Request.Body.
2. Getting Individual Pixels:
   Use img.At(x, y).RGBA() to retrieve the RGBA values for each pixel.
3. Building the Pixel Array:
   Construct a two-dimensional array pixels to represent the pixel arrangement. Iterate over each pixel in the image, adding its RGBA values to the corresponding row in pixels.
4. Converting to 8-Bit Representation:
   Since the RGBA values are 32-bit integers, divide them by 257 to get the 8-bit representation for the texImage2D method.

package main

import (
    "fmt"
    "image"
    "image/png"
    "os"
    "io"
    "net/http"
)

func main() {
    // Register other formats as needed
    image.RegisterFormat("png", "png", png.Decode, png.DecodeConfig)

    file, err := os.Open("./image.png")

    if err != nil {
        fmt.Println("Error: File could not be opened")
        os.Exit(1)
    }

    defer file.Close()

    pixels, err := getPixels(file)

    if err != nil {
        fmt.Println("Error: Image could not be decoded")
        os.Exit(1)
    }

    fmt.Println(pixels)
}

func getPixels(file io.Reader) ([][]Pixel, error) {
    img, _, err := image.Decode(file)

    if err != nil {
        return nil, err
    }

    bounds := img.Bounds()
    width, height := bounds.Max.X, bounds.Max.Y

    var pixels [][]Pixel
    for y := 0; y < height; y++ {
        var row []Pixel
        for x := 0; x < width; x++ {
            row = append(row, rgbaToPixel(img.At(x, y).RGBA()))
        }
        pixels = append(pixels, row)
    }

    return pixels, nil
}

func rgbaToPixel(r uint32, g uint32, b uint32, a uint32) Pixel {
    return Pixel{int(r / 257), int(g / 257), int(b / 257), int(a / 257)}
}

type Pixel struct {
    R int
    G int
    B int
    A int
}

By following these steps, you can effectively obtain a pixel array from an image for use with the texImage2D method in Go.

The above is the detailed content of How to Extract a Pixel Array from an Image in Go for `texImage2D`?. For more information, please follow other related articles on the PHP Chinese website!