All posts by stepan

Anti make install

What to do if you accidentally installed some experimental project to your system folder? Are here any ways to undo install script. Here is a simple solution.

Preamble

below may work or may not, this is all given as-is, you and only you are responsible person in case of some damage, data loss and so on. But I hope things go smooth!

To undo `make install` I would do (and I did) this:

Idea: check whatever script installs and undo this with simple bash script.

1. Reconfigure your build dir to install to some custom dir. I usually do this: `–prefix=$PWD/install`. For CMake, you can go to your build dir, open CMakeCache.txt, and fix CMAKE_INSTALL_PREFIX value.
2. Install project to custom directory (just run `make install` again).
3. Now we push from assumption, that `make install` script installs into custom dir just same contents you want to remove from somewhere else (usually `/usr/local`). So, we need a script.
3.1. Script should compare custom dir, with dir you want clean. I use this:

anti-install.sh

RM_DIR=$1
PRESENT_DIR=$2

echo "Remove files from $RM_DIR, which are present in $PRESENT_DIR"

pushd $RM_DIR

for fn in `find . -iname '*'`; do
# echo "Checking $PRESENT_DIR/$fn..."
if test -f "$PRESENT_DIR/$fn"; then
# First try this, and check whether things go plain
echo "rm $RM_DIR/$fn"

# Then uncomment this, (but, check twice it works good to you).
# rm $RM_DIR/$fn
fi
done

popd

3.2. Now just run this script (it will go dry-run)

bash anti-install.sh <dir you want to clean> <custom installation dir>

E.g. You wan’t to clean /usr/local, and your custom installation dir is /user/me/llvm.build/install, then it would be

bash anti-install.sh /usr/local /user/me/llvm.build/install

3.3. Check log carefully, if commands are good to you, uncomment `rm $RM_DIR/$fn` and run it again. But stop! Did you really check carefully? May be check again?

Good luck!

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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>

  template<
      typename OutputCollectionT,
      typename OutputItemT = typename OutputCollectionT::value_type
  >
  class Select {
  public:
      template<
          typename InputCollectionT,
          typename InputItemT = typename InputCollectionT::value_type
      >
      class From {
      public:
          static OutputCollectionT Do(
              const InputCollectionT &Input,
              std::function<OutputItemT(const InputItemT &In)> Selector
          ) {
            OutputCollectionT Out;
            for (const InputItemT &In : Input) {
              Out.push_back(Selector(In));
            }
            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) {
    std::cout
    << "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.

edge-detection.glsl
// 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);
#else
    return vec4(foreground.r, foreground.g, foreground.b, foregroundValue);
#endif
}

// 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),
        foregroundValue,
        edgeValue
    );
}
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