glReadPixels返回错误的值

Question

我尝试渲染像素颜色.

gl.glColor3f(1f, 0, 0);
//draw
gl.glReadPixels(lastX - pw / 2, MyCanvas.this.getHeight()
            - (lastY - ph / 2), pw, ph, GL.GL_RED, GL.GL_FLOAT,
            pixelBuffer);
float r, g, b;
r = pixelBuffer.getFloat();
g = pixelBuffer.getFloat();
b =pixelBuffer.getFloat();
pixelBuffer.rewind();
System.out.println(r+" "+g+" "+b);

屏幕上有真正的纯红色,但glReadPixels返回到非常奇怪的值4.6006E-41,为什么???

Answer 1

glReadPixels文件说:

glPixelStore设置的存储参数(如GL_PACK_LSB_FIRST和GL_PACK_SWAP_BYTES)会影响数据写入内存的方式.

所以检查你的glPixelStore配置.也就是说,您的字节顺序是向后的.

0x0000803F => 4.600602988224807e-41
0x3F800000 => 1.0

有用的链接:

• http://babbage.cs.qc.edu/IEEE-754/Decimal.html
• http://babbage.cs.qc.edu/IEEE-754/32bit.html