All posts by stepan

C++ sql-like Select example (imperfect)

I just would like to keep it here…

May be there is better implementation? Spent on it 30 mins, have no more time today.

// select.cpp

#include <vector>
#include <iostream>

      typename OutputCollectionT,
      typename OutputItemT = typename OutputCollectionT::value_type
  class Select {
          typename InputCollectionT,
          typename InputItemT = typename InputCollectionT::value_type
      class From {
          static OutputCollectionT Do(
              const InputCollectionT &Input,
              std::function<OutputItemT(const InputItemT &In)> Selector
          ) {
            OutputCollectionT Out;
            for (const InputItemT &In : Input) {
            return Out;

struct A {
    int P1;
    int P2;
    int P3;

struct B {
    int P1;
    int P3;

int main() {
  std::vector<A> aa = {
      {1, 2, 3},
      {2, 3, 4},
      {3, 4, 5}

  auto bb = Select<std::vector<B>>::From<std::vector<A>>::Do(
      aa, [=] (const A &a) -> B {
        return { a.P1, a.P3 };

  for (auto &b : bb) {
    << "P1:" << b.P1 << ", "
    << "P3:" << b.P3 << "\n";

  return 0;
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The music of waves (translation of Victor Tsoy song)

I have seen as waves wipe out the footprints on sand.
I have heard as wind sings his song of  the weird.
I have heard as trees strings playing this.

The music of waves.
The music of wind.

It’s hard to say here what the asphalt means.
It’s hard to say here what the vehicle means.
You have here to toss the water up.

The music of waves.
The music of wind.

Who of us remember those who stepped out the way?
Who of us remember those who laughed to sang.
Who of us remember feeling the coldness of gun butt…

The music of waves.
The music of wind.

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Edge detection shader for text

Hi there! I’m working on text rendering for my small Bird OSD project.

So I want to add contours to the text, so it could be visible whatever background it is rendered on (bright or dark).

For example I want to enhance text rendering for cases like this:

(Ugh… My eyes suffer!)

Into this one:

Assuming we have 1-component color on input which consists only of alpha channel, I want to mark as edge alpha values around 0.5.

Below is my shader which works, and in fact above are screenshots with its demonstraction. It still has some limits though. Edge radius  can’t take values ended with .5 due to special rounding case for N*0.5 values. If you use it, and find more issues, please let me know.

// The inpute textures
uniform sampler2D uTexture;
varying vec2 vTexCoord;  // Interpolated texture coordinate per fragment.

uniform float uOpacity;

uniform float uWidth;

uniform float uHeight;

// If foreground value is higher than threshold, than edge is zero for this pixel
const float NO_EDGE_TRESHOLD = 0.5;

// Edge radius, works fine in range from 0.6 to 2.0
// Please don't use N*0.5 values, since it has special rounding rules
// and pixel at the left may be in is not the same distance comparing to the right.
const float EDGE_RADIUS = 1.;

const vec3 EDGE = vec3(0., 0., 0.);

// Detects whether we should put edge value in the center.
// Not that if the center is foreground value = 1, then there is
// no need in edge
// (in practice we also admit some values below 1,
// determined by threshold).
// We work with fonts, not the regular image, so
// edge is a function from average of two pixels (not the difference):
// f(l, r) = edge((l + r) / 2)
//    assuming edge should be max, when input value is "k" (belongs to range (0, 1) )
// So, how 'edge' function is defined?
// (see picture if formulaes are difficult)
//    edge(v) = (1./k) * x, if x <= k && x > 0
//              otherwise it is line which goes through p1[x,y] = [1, k] and p2[x,y] = [0, 1]
//  Y ^
//    | p[y=1,x=k]
//    |  /\
//    | /  \
//    |/    \
//    ----------->
//    0  k  1    X
//    y=edge(x) formulae
// in case when k = 0.5 then
// f(l, r) = 1 - |l + r - 1|
// Let's use this case!
// params:
//    left - left foreground value
//    center - center foreground value
//    right - right foreground value
// returns:
//    edge value.
float getEdge(float left, float center, float right) {
    if (center > NO_EDGE_TRESHOLD)
        return 0.;

    if (center > left && center > right)
        return 0.;

    float ledge = 1. - abs(left + center - 1.);
    float redge = 1. - abs(right + center - 1.);

    return max(ledge, redge);

float getNeighbour(float row, float col) {
    float dx = EDGE_RADIUS / uWidth;
    float dy = EDGE_RADIUS / uHeight;

    float texX = clamp(vTexCoord.x + col * dx, 0. + dx/2., 1. - dx/2.);
    float texY = clamp(vTexCoord.y + row * dy, 0. + dx/2., 1. - dx/2.);

    return texture2D(uTexture, vec2(texX, texY)).a;

float calcEdge(float centerValue) {
    // Nighbour pixels:
    // neighbour[i][j] is neighbour with X = x + (j-1) * DX; Y = y + (i-1) * DY;
    // neighbour[0][0] is neighbour with X = x - DX; Y = y - DY;
    float neighbour_0[3];
    float neighbour_1[3];
    float neighbour_2[3];

    for (int j = 0; j != 3; ++j)
        neighbour_0[j] = getNeighbour(-1., float(j-1));

    for (int j = 0; j != 3; ++j)
        neighbour_1[j] = getNeighbour(0., float(j-1));

    for (int j = 0; j != 3; ++j)
        neighbour_2[j] = getNeighbour(1., float(j-1));

    float horEdge = getEdge(neighbour_1[0], centerValue, neighbour_1[2]);
    float vertEdge = getEdge(neighbour_0[1], centerValue, neighbour_2[1]);
    float ltrbEdge = getEdge(neighbour_0[0], centerValue, neighbour_2[2]);
    float rtlbEdge = getEdge(neighbour_0[2], centerValue, neighbour_2[0]);

    return max( max(horEdge, vertEdge), max(ltrbEdge, rtlbEdge) );

vec4 calcFinalValue(vec3 foreground, float foregroundValue, float edgeValue) {
#if 1
    float sumFgEdge = foregroundValue + edgeValue;
    vec3 color = vec3(
        foreground * foregroundValue / sumFgEdge +
        EDGE * edgeValue / sumFgEdge);

    return vec4(color.r, color.g, color.b, min(sumFgEdge, 1. * uOpacity));

    //return vec4(EDGE, edgeValue);
    return vec4(foreground.r, foreground.g, foreground.b, foregroundValue);

// The entry point for our fragment shader.
void main()
    vec4 texColor = texture2D(uTexture, vTexCoord);

    float foregroundValue = texColor.a;
    float edgeValue = calcEdge(foregroundValue);

    gl_FragColor = calcFinalValue(
        vec3(texColor.r, texColor.g, texColor.b),
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Прошу прощенья у тебя
За то, что ем беспечно плюшки
Чизкейки, пироги, ватружки,
Всякие там кренделя.
И взвешиваться мне каждый раз –
Не нужно.

Жестоко может быть порой –
С тоской
Стыдливою любя
Отжаться двадцать раз отправлю,
И столько же  еще присесть,
За пару долек шоколадки,
Что ты успела есть.

И беспощадно но с теплом,
Заставлю сделать пресс раз тридцать.
За блинчик вкусный, что в твоем
Прекрасном теле очутился
Так внезапно!
Запитый рафом с имбирем.

За пищи нетождественный прием –
Сгорает еда мигом в животе моем,
Я – дрищ (вдобавок малость нервный),
А  тебя –


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Невычислимая ласковость

Все слышали слово “вкусняшка”. Теперь иногда говорят “вкусняшечка”. А недавно я услышал “вкуняшечечка”. В какой-то момент эти ласковые личности, подобно тем самым невычислимым машинам Тьюринга не смогут остановиться и будут до конца времен произносить “чечечечечече…”.
А еще…
Будте внимательны, набирая в своих телефончиках слово “машинка”. Приходилось видеть и такое в чатах.

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Чередование симметрии

М: Вы кто?
Н: А вы кто?
М: Гм… Здесь что эхо?!
Н: Нет, просто наши голоса похожи, и я вам задал тот же самый вопрос, что и вы мне. Вам показалось.
М: Да это же был сарказм!
Н: Вынужден признать – да – это был сарказм, не смог удержаться, приношу свои извинения.

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