lookup table 256*16 24 bit issue

[delux-soft]

I write this code for 256*16 table, it works fine with 32-bit color but produce wrong result with 24-bit color.

"varying highp vec2 textureCoordinate;\n" +
" varying highp vec2 textureCoordinate2; // TODO: This is not used\n" +
" \n" +
" uniform sampler2D inputImageTexture;\n" +
" uniform sampler2D inputImageTexture2; // lookup texture\n" +
" \n" +
" uniform lowp float intensity;\n" +
" \n" +
"void main() {" +
" highp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);\n" +
" \n" +
" highp float blueColor = textureColor.b * 15.0;\n" +
" \n" +
" highp vec2 quad1;\n" +
" quad1.y = floor(floor(blueColor) / 1.0);\n" +
" quad1.x = floor(blueColor) - (quad1.y * 16.0);\n" +
" \n" +
" highp vec2 quad2;\n" +
" quad2.y = floor(ceil(blueColor) / 1.0);\n" +
" quad2.x = ceil(blueColor) - (quad2.y * 16.0);\n" +
" \n" +
" highp vec2 texPos1;\n" +
" texPos1.x = (quad1.x * 0.0625) + 0.5/256.0 + ((0.0625 - 1.0/256.0) * textureColor.r);\n" +
" texPos1.y = (quad1.y * 1.0) + 0.5/16.0 + ((1.0 - 1.0/16.0) * textureColor.g);\n" +
" \n" +
" highp vec2 texPos2;\n" +
" texPos2.x = (quad2.x * 0.0625) + 0.5/256.0 + ((0.0625 - 1.0/256.0) * textureColor.r);\n" +
" texPos2.y = (quad2.y * 1.0) + 0.5/16.0 + ((1.0 - 1.0/16.0) * textureColor.g);\n" +
" \n" +
" lowp vec4 newColor1 = texture2D(inputImageTexture2, texPos1);\n" +
" lowp vec4 newColor2 = texture2D(inputImageTexture2, texPos2);\n" +
" \n" +
" lowp vec4 newColor = mix(newColor1, newColor2, fract(blueColor));\n" +
" gl_FragColor = mix(textureColor, vec4(newColor.rgb, textureColor.w), intensity);\n" +
"}"