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Drawing on an image

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In this example we see how to generate vector graphics in two different contexts using the same drawing code (Figure 1). On the left side we render directly into the window through a View control. On the right side generate an image using different resolutions. To show it we use a ImageView control configured to stretch the image in case it is smaller than the control itself, which makes clear the loss of quality. The source code is in folder /src/howto/drawimg of the SDK distribution.

Application where different drawing contexts are used.
Figure 1: 2D Contexts: Window (left), Image (right).
Macos version of application.
Figure 2: macOS version.
Linux version of application.
Figure 3: Linux version.
Listing 1: howto/drawimg/drawimg.c
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/* Drawing on an image */

#include "nappgui.h"
#include "allres.h"

typedef struct _app_t App;

struct _app_t
{
    Window *window;
    Font *font;
    View *view;
    ImageView *iview;
    uint32_t res;
    real32_t angle;
    real32_t scale;
};

static uint32_t i_WIDTH[4] = {600, 300, 150, 75};
static uint32_t i_HEIGHT[4] = {400, 200, 100, 50};
static real32_t i_SCALE[4] = {1, .5f, .25f, .125f};

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

static void i_draw(DCtx *ctx, const T2Df *t2d_global, const Font *font)
{
    T2Df t2d_object;
    V2Df triangle[] = { {472,0}, {600,144}, {344,144} };
    const Image *image1 = gui_image(MONKEY_GIF);
    const Image *image2 = gui_image(ZOMBIE_PNG);
    t2d_scalef(&t2d_object, t2d_global, .5f, .5f);
    draw_matrix(ctx, &t2d_object);
    draw_image(ctx, image1, 688, 288);
    draw_line_color(ctx, color_rgb(255, 0, 0));
    draw_line_width(ctx, 3);
    draw_fill_color(ctx, color_rgb(0, 0, 255));
    t2d_rotatef(&t2d_object, t2d_global, kBMATH_PIf / 4);
    draw_matrix(ctx, &t2d_object);
    draw_rect(ctx, ekSKFILL, 0, 0, 320, 200);
    draw_fill_color(ctx, color_rgb(0, 255, 0));
    draw_matrix(ctx, t2d_global);
    draw_circle(ctx, ekSKFILL, 300, 200, 100);
    draw_line_color(ctx, color_rgb(0, 0, 255));
    draw_fill_color(ctx, color_rgb(255, 0, 0));
    draw_polygon(ctx, ekSKFILL, triangle, 3);
    t2d_scalef(&t2d_object, t2d_global, .7f, .7f);
    draw_matrix(ctx, &t2d_object);
    draw_image(ctx, image2, 0, 0);
    draw_font(ctx, font);
    draw_matrix(ctx, t2d_global);
    draw_text_color(ctx, color_rgb(255, 0, 0));
    draw_text(ctx, "Hello Drawings!", 200, 15);
    draw_line_color(ctx, color_rgb(0, 128, 0));
    draw_line(ctx, 150, 350, 330, 350);
    draw_line_color(ctx, color_rgb(0, 0, 255));
    draw_line(ctx, 100, 370, 330, 370);
    draw_line_color(ctx, color_rgb(128, 0, 0));
    draw_line(ctx, 20, 390, 330, 390);
}

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

static void i_OnDraw(App *app, Event *e)
{
    T2Df t2d;
    const EvDraw *p = event_params(e, EvDraw);
    t2d_rotatef(&t2d, kT2D_IDENTf, app->angle);
    t2d_scalef(&t2d, &t2d, app->scale, 1);
    draw_clear(p->ctx, color_rgb(200, 200, 200));
    i_draw(p->ctx, &t2d, app->font);
}

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

static void i_draw_img(App *app)
{
    T2Df t2d;
    DCtx *ctx = dctx_bitmap(i_WIDTH[app->res], i_HEIGHT[app->res], ekRGB24);
    Image *image;
    t2d_scalef(&t2d, kT2D_IDENTf, i_SCALE[app->res], i_SCALE[app->res]);
    draw_clear(ctx, color_rgb(200, 200, 200));
    i_draw(ctx, &t2d, app->font);
    image = dctx_image(&ctx);
    imageview_image(app->iview, image);
    image_destroy(&image);
}

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

static void i_OnResolution(App *app, Event *e)
{
    const EvButton *p = event_params(e, EvButton);
    app->res = p->index;
    i_draw_img(app);
}

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

static Layout *i_img_layout(App *app)
{
    Layout *layout = layout_create(5, 1);
    Label *label = label_create();
    Button *button1 = button_radio();
    Button *button2 = button_radio();
    Button *button3 = button_radio();
    Button *button4 = button_radio();
    label_text(label, "Image context:");
    button_text(button1, "600x400");
    button_text(button2, "300x200");
    button_text(button3, "150x100");
    button_text(button4, "75x50");
    button_state(button1, ekON);
    button_OnClick(button1, listener(app, i_OnResolution, App));
    layout_label(layout, label, 0, 0);
    layout_button(layout, button1, 1, 0);
    layout_button(layout, button2, 2, 0);
    layout_button(layout, button3, 3, 0);
    layout_button(layout, button4, 4, 0);
    layout_hmargin(layout, 0, 5);
    layout_hmargin(layout, 1, 10);
    layout_hmargin(layout, 2, 10);
    layout_hmargin(layout, 3, 10);
    return layout;
}

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

static void i_OnAngle(App *app, Event *e)
{
    const EvSlider *p = event_params(e, EvSlider);
    app->angle = (p->pos - .5f) * kBMATH_PIf;
    view_update(app->view);
}

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

static void i_OnScale(App *app, Event *e)
{
    const EvSlider *p = event_params(e, EvSlider);
    app->scale = p->pos + .5f;
    view_update(app->view);
}

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

static Layout *i_win_layout(App *app)
{
    Layout *layout = layout_create(3, 1);
    Label *label = label_create();
    Slider *slider1 = slider_create();
    Slider *slider2 = slider_create();
    label_text(label, "Window context: 600x400");
    slider_value(slider1, .5f);
    slider_value(slider2, .5f);
    slider_OnMoved(slider1, listener(app, i_OnAngle, App));
    slider_OnMoved(slider2, listener(app, i_OnScale, App));
    layout_label(layout, label, 0, 0);
    layout_slider(layout, slider1, 1, 0);
    layout_slider(layout, slider2, 2, 0);
    layout_hmargin(layout, 0, 10);
    layout_hmargin(layout, 1, 10);
    layout_hexpand2(layout, 1, 2, .5f);
    return layout;
}

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

static Panel *i_panel(App *app)
{
    Panel *panel = panel_create();
    Layout *layout = layout_create(2, 2);
    Layout *wlayout = i_win_layout(app);
    Layout *ilayout = i_img_layout(app);
    View *view = view_create();
    ImageView *iview = imageview_create();
    view_size(view, s2df(600, 400));
    imageview_size(iview, s2df(600, 400));
    view_OnDraw(view, listener(app, i_OnDraw, App));
    imageview_scale(iview, ekASPECT);
    layout_layout(layout, wlayout, 0, 0);
    layout_view(layout, view, 0, 1);
    layout_imageview(layout, iview, 1, 1);
    layout_layout(layout, ilayout, 1, 0);
    layout_halign(layout, 1, 0, ekLEFT);
    layout_margin(layout, 10);
    layout_hmargin(layout, 0, 5);
    layout_vmargin(layout, 0, 5);
    panel_layout(panel, layout);
    app->view = view;
    app->iview = iview;
    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);
    Panel *panel = i_panel(app);
    gui_respack(allres_respack);
    gui_language("");
    app->window = window_create(ekWNSTD, &panel);
    app->font = font_system(25.f, 0);
    app->res = 0;
    app->angle = 0;
    app->scale = 1;
    i_draw_img(app);
    window_title(app->window, "Drawing on an image");
    window_origin(app->window, v2df(500, 200));
    window_OnClose(app->window, listener(app, i_OnClose, App));
    window_show(app->window);
    return app;
}

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

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

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

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