How to Retrieve a Pixel Array from a Go `image.Image` for OpenGL ES 2.0?

Pixel Array Retrieval from Go Image.Image

In Go, the image.Image interface represents an image containing pixel data. To obtain a pixel array from an image.Image for use in OpenGL ES 2.0 via the texImage2D method, you can use the following steps:

1. Define a custom Pixel struct to represent individual pixels:

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

2. Create a function, rgbaToPixel, to convert RGBA values to a Pixel struct:

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)}
}

3. Write a function, getPixels, to extract the pixel array from the image.Image:

func getPixels(img image.Image) ([][]Pixel, error) {
    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
}

4. Load an image and call getPixels to obtain the pixel array:

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)
}

5. Use pixels to pass to the texImage2D method as needed.

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