shader
            
            
              glsl
              
              
            
          
          #version 320 es
precision highp float;
in  vec2 TexCoord;
out vec4 FragColor;
// texture sampler
uniform sampler2D texture_diffuse1;
uniform vec2 textureOffset;
void main()
{
	vec2 position = vec2(4.0/8.0, 1.0/8.0);
	vec2 size     = vec2(1.0/8.0, 1.0/8.0);
	
	// 计算1,显示清晰
	vec2 uv = position + size * fract(TexCoord);
	FragColor = texture(texture_diffuse1, uv);
	
	// 计算2, 显示模糊
	vec2 dx = dFdx(TexCoord);
	vec2 dy = dFdy(TexCoord);
	vec2 uv = position + size * fract(TexCoord);
	FragColor = textureGrad(texture_diffuse1, uv, dx, dy);
	
}