Why is my collision detection not accurate?

Question

After trying and trying, I still cannot understand why the leg of character exceeds the wall but no clipping issue when I hit the wall from below. How should I fix it to make him stand still on the wall?

From collideWithBox() function below, it shows that playerDest.Y = boxDest.Y - boxDest.height; will get the position the character should standstill on the wall. Theoretically, the clipping effect won't be happen as the character hit the box from below works with the equation playerDest.Y = boxDest.Y + boxDest.height;.

void collideWithBox()
{
    if ( spriteCollide(playerDest, boxDest) && keyArr[VK_UP])
        //playerDest.Y += 50;
        playerDest.Y = boxDest.Y + boxDest.height;
    else if ( spriteCollide(playerDest, boxDest) && !keyArr[VK_UP])
        playerDest.Y = boxDest.Y - boxDest.height;
}



void initPlayer()
{
    //  Create texture.
    hr = D3DXCreateTextureFromFileEx(d3dDevice, "player.png", 169, 44, 
        D3DX_DEFAULT, NULL, D3DFMT_A8R8G8B8, D3DPOOL_MANAGED, 
        D3DX_DEFAULT, D3DX_DEFAULT, D3DCOLOR_XRGB(255, 255, 255), 
        NULL, NULL, &player);

    playerRect.left = playerRect.top = 0;
    playerRect.right = 29; 
    playerRect.bottom = 36;

    playerDest.X  = 0; 
    playerDest.Y  = 564;

    playerDest.length = playerRect.right - playerRect.left;
    playerDest.height = playerRect.bottom - playerRect.top;
}

void initBox()
{
    hr = D3DXCreateTextureFromFileEx(d3dDevice, "brock.png", 330, 132, 
        D3DX_DEFAULT, NULL, D3DFMT_A8R8G8B8, D3DPOOL_MANAGED, 
        D3DX_DEFAULT, D3DX_DEFAULT, D3DCOLOR_XRGB(255, 255, 255), 
        NULL, NULL, &box);

    boxRect.left = 33;
    boxRect.top = 0;
    boxRect.right = 63; 
    boxRect.bottom = 30;

    boxDest.X = boxDest.Y = 300;

    boxDest.length = boxRect.right - boxRect.left;
    boxDest.height = boxRect.bottom - boxRect.top;
}

bool spriteCollide(Entity player, Entity target)
{
    float left1, left2;
    float right1, right2;
    float top1, top2;
    float bottom1, bottom2;

    left1 = player.X;
    left2 = target.X;
    right1 = player.X + player.length;
    right2 = target.X + target.length;

    top1 = player.Y;
    top2 = target.Y;

    bottom1 = player.Y + player.height;
    bottom2 = target.Y + target.height;

    if (bottom1 < top2) return false;
    if (top1 > bottom2) return false;

    if (right1 < left2) return false;
    if (left1 > right2) return false;

    return true;
}

Answer 1

playerDest.Y = boxDest.Y - boxDest.height

should be

playerDest.Y = boxDest.Y - playerDest.height