UV coordinates to Pixel coordinates

Posted 2020-12-21 d1012181765

pix.x = (uv.x * texture.width) -0.5
pix.y = ((1-uv.y) * texture.height) -0.5

uv坐标的y轴与图像上的像素坐标相反
对于最近的邻插值，只需舍入像素坐标
对于双线性插值，请从四个相邻像素计算参与百分比并进行加权平均
当UV坐标超出范围时，可以选择如何处理“纹理包裹”：opengl texture Wrapping
这是一些带有“重复”纹理包装的双线性插值的Java代码：

private static int billinearInterpolation(Point2D uv, BufferedImage texture) {
    uv.x = uv.x>0 ? uv.x%1 : 1+(uv.x%1);
    uv.y = uv.y>0 ? uv.y%1 : 1+(uv.y%1);
    double pixelXCoordinate = uv.x * texture.getWidth() - 0.5;
    double pixelYCoordinate = (1-uv.y) * texture.getHeight() - 0.5;

    pixelXCoordinate = pixelXCoordinate<0?texture.getWidth()-pixelXCoordinate: pixelXCoordinate;
    pixelYCoordinate = pixelYCoordinate<0?texture.getHeight()-pixelYCoordinate : pixelYCoordinate;

    int x = (int) Math.floor(pixelXCoordinate);
    int y = (int) Math.floor(pixelYCoordinate);

    double pX = pixelXCoordinate - x;
    double pY = pixelYCoordinate - y;

    float[] px = new float[]{(float) (1 - pX), (float) pX};
    float[] py = new float[]{(float) (1 - pY), (float) pY};

    float red = 0;
    float green = 0;
    float blue = 0;
    float alpha = 0;
    for (int i = 0; i < px.length; i++) {
        for (int j = 0; j < py.length; j++) {
            float p = px[i] * py[j];
            if (p != 0) {
                int rgb = texture.getRGB((x + i)%texture.getWidth(), (y + j)%texture.getHeight());
                alpha += (float) ((rgb >> 24) & 0xFF) * p;
                red += (float) ((rgb >> 16) & 0xFF) * p;
                green += (float) ((rgb >> 8) & 0xFF) * p;
                blue += (float) ((rgb >> 0) & 0xFF) * p;
            }
        }
    }
    return (((int) alpha & 0xFF) << 24) |
            (((int) red & 0xFF) << 16) |
            (((int) green & 0xFF) << 8) |
            (((int) blue & 0xFF) << 0);
}