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SDK Multiplataforma en C

Filters

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Además de la generación procedimental de imágenes, la manipulación directa de píxeles tiene otra gran utilidad: La aplicación de filtros. Para ello, en primer lugar, obtendremos un búfer con el valor original de los píxeles mediante image_pixels. Un filtro no es más que una función que cambia el color de cada punto para lograr el efecto deseado. En este ejemplo implementamos el algoritmo de convolución el cual necesita conocer el entorno de vecindad de cada punto para procesar el efecto (Figura 1). En función de los valores asignados a la matriz de convolución obtendremos diferentes resultados. El código fuente está en la caperta /src/demo/filters de la distribución del SDK.

  • Utiliza image_from_pixels para crear una nueva imagen con los píxeles modificados.
  • Captura de una aplicación con filtros de imagen. Versión Windows.
    Figura 1: Aplicación Filters, versión Windows.
    Captura de una aplicación con filtros de imagen. Versión macOS.
    Figura 2: Versión macOS.
    Captura de una aplicación con filtros de imagen. Versión Linux.
    Figura 3: Versión Linux.
Listado 1: demo/filters/filters.c
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/* NAppGUI Hello World */

#include "nappgui.h"
#include "all.h"

typedef struct _app_t App;

struct _app_t
{
    Window *window;
    Image *image;
    ImageView *view;
    Cell *slider;
    uint32_t filter;
    real32_t angle;
};

/*---------------------------------------------------------------------------*/

static const uint32_t i_IDENT_SIZE = 3;
static const real32_t i_IDENT_FACTOR = 1;
static const real32_t i_IDENT_BIAS = 0;
static const real32_t i_IDENT_FILTER[] =
{
    0, 0, 0,
    0, 1, 0,
    0, 0, 0
};


static const uint32_t i_BLUR_SIZE = 5;
static const real32_t i_BLUR_FACTOR = 1.f / 256.f;
static const real32_t i_BLUR_BIAS = 0;
static const real32_t i_BLUR_FILTER[] =
{
    1,  4,  6,  4,  1,
    4, 16, 24, 16,  4,
    6, 24, 36, 24,  6,
    4, 16, 24, 16,  4,
    1,  4,  6,  4,  1,
};

static const uint32_t i_MOTION_SIZE = 9;
static const real32_t i_MOTION_FACTOR = 1.f / 9.f;
static const real32_t i_MOTION_BIAS = 0;
static const real32_t i_MOTION_FILTER[] =
{
  1, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 1, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 1, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 1, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 1, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 1, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 1, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 1, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 1,
};

static const uint32_t i_EDGE_SIZE = 5;
static const real32_t i_EDGE_FACTOR = 1;
static const real32_t i_EDGE_BIAS = 0;
static const real32_t i_EDGE_FILTER[] =
{
    -1,  0,  0,  0,  0,
    0, -2,  0,  0,  0,
    0,  0,  6,  0,  0,
    0,  0,  0, -2,  0,
    0,  0,  0,  0, -1,
};

static const uint32_t i_SHARPEN_SIZE = 3;
static const real32_t i_SHARPEN_FACTOR = 1;
static const real32_t i_SHARPEN_BIAS = 0;
static const real32_t i_SHARPEN_FILTER[] =
{
    1, 1, 1,
    1, -7, 1,
    1, 1, 1
};

static const uint32_t i_EMBOSS_SIZE = 3;
static const real32_t i_EMBOSS_FACTOR = 1;
static const real32_t i_EMBOSS_BIAS = 128;
static const real32_t i_EMBOSS_FILTER[] =
{
    -1, -1,  0,
    -1,  0,  1,
    0,  1,  1
};

/*---------------------------------------------------------------------------*/

static void i_apply_filter(App *app)
{
    Pixbuf *pixbuf = NULL;
    Pixbuf *output = NULL;
    Image *image = NULL;

    image_pixels(app->image, ekFIMAGE, &pixbuf, NULL);

    switch (app->filter) {
    case 0:
        output = pixbuf_convolution(pixbuf, i_IDENT_FILTER, i_IDENT_SIZE, i_IDENT_SIZE, i_IDENT_FACTOR, i_IDENT_BIAS);
        break;
    case 1:
        output = pixbuf_convolution(pixbuf, i_BLUR_FILTER, i_BLUR_SIZE, i_BLUR_SIZE, i_BLUR_FACTOR, i_BLUR_BIAS);
        break;
    case 2:
        output = pixbuf_convolution(pixbuf, i_MOTION_FILTER, i_MOTION_SIZE, i_MOTION_SIZE, i_MOTION_FACTOR, i_MOTION_BIAS);
        break;
    case 3:
        output = pixbuf_convolution(pixbuf, i_EDGE_FILTER, i_EDGE_SIZE, i_EDGE_SIZE, i_EDGE_FACTOR, i_EDGE_BIAS);
        break;
    case 4:
        output = pixbuf_convolution(pixbuf, i_SHARPEN_FILTER, i_SHARPEN_SIZE, i_SHARPEN_SIZE, i_SHARPEN_FACTOR, i_SHARPEN_BIAS);
        break;
    case 5:
        output = pixbuf_convolution(pixbuf, i_EMBOSS_FILTER, i_EMBOSS_SIZE, i_EMBOSS_SIZE, i_EMBOSS_FACTOR, i_EMBOSS_BIAS);
        break;
    case 6:
        output = pixbuf_rotate(pixbuf, (real32_t)(pixbuf_width(pixbuf) / 2), (real32_t)(pixbuf_height(pixbuf) / 2), app->angle * kBMATH_PIf, TRUE, color_gray(240));
        break;
    cassert_default();
    }

    cell_enabled(app->slider, app->filter == 6);
    image = image_from_pixbuf(output, NULL);
    imageview_image(app->view, image);
    pixbuf_destroy(&pixbuf);
    pixbuf_destroy(&output);
    image_destroy(&image);
}

/*---------------------------------------------------------------------------*/

static void i_OnButton(App *app, Event *e)
{
    const EvButton *p = event_params(e, EvButton);
    app->filter = p->index;
    i_apply_filter(app);
}

/*---------------------------------------------------------------------------*/

static void i_OnSlider(App *app, Event *e)
{
    const EvSlider *p = event_params(e, EvSlider);
    app->angle = p->pos;
    i_apply_filter(app);
}

/*---------------------------------------------------------------------------*/

static Panel *i_panel(App *app)
{
    Panel *panel = panel_create();
    Layout *layout1 = layout_create(1, 2);
    Layout *layout2 = layout_create(8, 1);
    Layout *layout3 = layout_create(2, 1);
    Button *button1 = button_radio();
    Button *button2 = button_radio();
    Button *button3 = button_radio();
    Button *button4 = button_radio();
    Button *button5 = button_radio();
    Button *button6 = button_radio();
    Button *button7 = button_radio();
    Slider *slider = slider_create();
    ImageView *view1 = imageview_create();
    ImageView *view2 = imageview_create();
    uint32_t w, h;
    button_text(button1, "Identity");
    button_text(button2, "Blur");
    button_text(button3, "Motion");
    button_text(button4, "Edge");
    button_text(button5, "Sharpen");
    button_text(button6, "Emboss");
    button_text(button7, "Rotation");
    button_state(button3, ekON);
    button_OnClick(button1, listener(app, i_OnButton, App));
    slider_OnMoved(slider, listener(app, i_OnSlider, App));
    image_size(app->image, &w, &h);
    imageview_image(view1, app->image);
    imageview_image(view2, app->image);
    imageview_size(view1, s2di(w, h));
    imageview_size(view2, s2di(w, h));
    layout_button(layout2, button1, 0, 0);
    layout_button(layout2, button2, 1, 0);
    layout_button(layout2, button3, 2, 0);
    layout_button(layout2, button4, 3, 0);
    layout_button(layout2, button5, 4, 0);
    layout_button(layout2, button6, 5, 0);
    layout_button(layout2, button7, 6, 0);
    layout_slider(layout2, slider, 7, 0);
    layout_imageview(layout3, view1, 0, 0);
    layout_imageview(layout3, view2, 1, 0);
    layout_layout(layout1, layout2, 0, 0);
    layout_layout(layout1, layout3, 0, 1);
    layout_margin(layout1, 10);
    layout_hmargin(layout2, 0, 15);
    layout_hmargin(layout2, 1, 15);
    layout_hmargin(layout2, 2, 15);
    layout_hmargin(layout2, 3, 15);
    layout_hmargin(layout2, 4, 15);
    layout_hmargin(layout2, 5, 15);
    layout_vmargin(layout1, 0, 5);
    layout_hmargin(layout3, 0, 5);
    layout_hexpand(layout2, 7);
    panel_layout(panel, layout1);
    app->slider = layout_cell(layout2, 7, 0);
    app->view = view2;
    return panel;
}

/*---------------------------------------------------------------------------*/

static void i_OnClose(App *app, Event *e)
{
    osapp_finish();
    unref(app);
    unref(e);
}

/*---------------------------------------------------------------------------*/

static App *i_create(void)
{
    App *app = heap_new0(App);
    ResPack *pack = all_respack("");
    Panel *panel = NULL;
    app->image = image_copy(image_from_resource(pack, IMAGE_JPG));
    panel = i_panel(app);
    app->window = window_create(ekWNSTD, &panel);
    app->filter = 2;
    i_apply_filter(app);
    window_title(app->window, "Image Filters");
    window_origin(app->window, v2df(500, 200));
    window_OnClose(app->window, listener(app, i_OnClose, App));
    window_show(app->window);
    respack_destroy(&pack);
    return app;
}

/*---------------------------------------------------------------------------*/

static void i_destroy(App **app)
{
    window_destroy(&(*app)->window);
    image_destroy(&(*app)->image);
    heap_delete(app, App);
}

/*---------------------------------------------------------------------------*/

#include "osmain.h"
osmain(i_create, i_destroy, "", App)
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