option for screen filtering mode

src/shaders/hq2x.frag

@@ -0,0 +1,87 @@
+// This float value should be defined from the compiling code.
+// #define SCALE [2, 3, 4].0
+
+#version 150
+#ifdef GL_ES
+    #define PRECISION mediump
+    precision PRECISION float;
+    precision PRECISION int;
+#else
+    #define PRECISION
+#endif
+#define SCALE 2.0
+
+uniform sampler2D u_texture;
+uniform sampler2D u_lut;
+uniform vec2 u_textureSize;
+
+in vec4 v_texCoord[4];
+
+const mat3 YUV_MATRIX = mat3(0.299, 0.587, 0.114, -0.169, -0.331, 0.5, 0.5, -0.419, -0.081);
+const vec3 YUV_THRESHOLD = vec3(48.0/255.0, 7.0/255.0, 6.0/255.0);
+const vec3 YUV_OFFSET = vec3(0, 0.5, 0.5);
+
+out vec4 fragColor;
+
+bool diff(vec3 yuv1, vec3 yuv2) {
+    return any(greaterThan(abs((yuv1 + YUV_OFFSET) - (yuv2 + YUV_OFFSET)), YUV_THRESHOLD));
+}
+
+mat3 transpose(mat3 val) {
+    mat3 result;
+    result[0][1] = val[1][0];
+    result[0][2] = val[2][0];
+    result[1][0] = val[0][1];
+    result[1][2] = val[2][1];
+    result[2][0] = val[0][2];
+    result[2][1] = val[1][2];
+    return result;
+}
+
+void main() {
+    vec2 fp = fract(v_texCoord[0].xy * u_textureSize);
+    vec2 quad = sign(-0.5 + fp);
+    mat3 yuv = transpose(YUV_MATRIX);
+
+    float dx = v_texCoord[0].z;
+    float dy = v_texCoord[0].w;
+    vec3 p1  = texture(u_texture, v_texCoord[0].xy).rgb;
+    vec3 p2  = texture(u_texture, v_texCoord[0].xy + vec2(dx, dy) * quad).rgb;
+    vec3 p3  = texture(u_texture, v_texCoord[0].xy + vec2(dx, 0) * quad).rgb;
+    vec3 p4  = texture(u_texture, v_texCoord[0].xy + vec2(0, dy) * quad).rgb;
+    // Use mat4 instead of mat4x3 here to support GLES.
+    mat4 pixels = mat4(vec4(p1, 0.0), vec4(p2, 0.0), vec4(p3, 0.0), vec4(p4, 0.0));
+
+    vec3 w1  = yuv * texture(u_texture, v_texCoord[1].xw).rgb;
+    vec3 w2  = yuv * texture(u_texture, v_texCoord[1].yw).rgb;
+    vec3 w3  = yuv * texture(u_texture, v_texCoord[1].zw).rgb;
+
+    vec3 w4  = yuv * texture(u_texture, v_texCoord[2].xw).rgb;
+    vec3 w5  = yuv * p1;
+    vec3 w6  = yuv * texture(u_texture, v_texCoord[2].zw).rgb;
+
+    vec3 w7  = yuv * texture(u_texture, v_texCoord[3].xw).rgb;
+    vec3 w8  = yuv * texture(u_texture, v_texCoord[3].yw).rgb;
+    vec3 w9  = yuv * texture(u_texture, v_texCoord[3].zw).rgb;
+
+    bvec3 pattern[3];
+    pattern[0] =  bvec3(diff(w5, w1), diff(w5, w2), diff(w5, w3));
+    pattern[1] =  bvec3(diff(w5, w4), false       , diff(w5, w6));
+    pattern[2] =  bvec3(diff(w5, w7), diff(w5, w8), diff(w5, w9));
+    bvec4 cross = bvec4(diff(w4, w2), diff(w2, w6), diff(w8, w4), diff(w6, w8));
+
+    vec2 index;
+    index.x = dot(vec3(pattern[0]), vec3(1, 2, 4)) +
+    dot(vec3(pattern[1]), vec3(8, 0, 16)) +
+    dot(vec3(pattern[2]), vec3(32, 64, 128));
+    index.y = dot(vec4(cross), vec4(1, 2, 4, 8)) * (SCALE * SCALE) +
+    dot(floor(fp * SCALE), vec2(1.0, SCALE));
+
+    vec2 step = vec2(1.0) / vec2(256.0, 16.0 * (SCALE * SCALE));
+    vec2 offset = step / vec2(2.0);
+    vec4 weights = texture(u_lut, index * step + offset);
+    float sum = dot(weights, vec4(1));
+    vec3 res = (pixels * (weights / sum)).rgb;
+
+    fragColor.rgb = res;
+}

src/shaders/hq2x.vert

@@ -0,0 +1,41 @@
+#version 150
+#ifdef GL_ES
+    #define PRECISION mediump
+    precision PRECISION float;
+    precision PRECISION int;
+#else
+    #define PRECISION
+#endif
+
+in vec4 a_position;
+in vec2 a_texCoord0;
+
+uniform mat4 u_projTrans;
+
+out vec2 u_textureSize;
+out vec4 v_texCoord[4];
+
+void main() {
+    gl_Position = u_projTrans * a_position;
+
+    vec2 ps = 1.0/u_textureSize;
+    float dx = ps.x;
+    float dy = ps.y;
+
+    //   +----+----+----+
+    //   |    |    |    |
+    //   | w1 | w2 | w3 |
+    //   +----+----+----+
+    //   |    |    |    |
+    //   | w4 | w5 | w6 |
+    //   +----+----+----+
+    //   |    |    |    |
+    //   | w7 | w8 | w9 |
+    //   +----+----+----+
+
+    v_texCoord[0].zw = ps;
+    v_texCoord[0].xy = a_texCoord0.xy;
+    v_texCoord[1] = a_texCoord0.xxxy + vec4(-dx, 0, dx, -dy); //  w1 | w2 | w3
+    v_texCoord[2] = a_texCoord0.xxxy + vec4(-dx, 0, dx,   0); //  w4 | w5 | w6
+    v_texCoord[3] = a_texCoord0.xxxy + vec4(-dx, 0, dx,  dy); //  w7 | w8 | w9
+}