snapshot_resize.c

#include <assert.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include "bcm_host.h"

void
takeSnapshot(
    DISPMANX_DISPLAY_HANDLE_T display,
    DISPMANX_MODEINFO_T *info,
    VC_IMAGE_TYPE_T type,
    int width,
    int height,
    int pitch,
    void *buffer)
{
    uint32_t vc_image_ptr;
    DISPMANX_RESOURCE_HANDLE_T resource =
        vc_dispmanx_resource_create(type,
                                    width,
                                    height,
                                    &vc_image_ptr);

    vc_dispmanx_snapshot(display, resource, DISPMANX_NO_ROTATE);
    VC_RECT_T rect;
    vc_dispmanx_rect_set(&rect, 0, 0, width, height);
    vc_dispmanx_resource_read_data(resource, &rect, buffer, pitch);

    int result = vc_dispmanx_resource_delete(resource);
    assert(result == 0);
}

void
showSnapshot(
    DISPMANX_DISPLAY_HANDLE_T display,
    DISPMANX_MODEINFO_T *info,
    VC_IMAGE_TYPE_T type,
    int width,
    int height,
    int pitch,
    void *buffer)
{
    uint32_t vc_image_ptr;

    DISPMANX_RESOURCE_HANDLE_T resource =
        vc_dispmanx_resource_create(type, width, height, &vc_image_ptr);
    assert(resource != 0);

    VC_RECT_T dst_rect;
    vc_dispmanx_rect_set(&dst_rect, 0, 0, width, height);

    int result = vc_dispmanx_resource_write_data(resource,
                                                 type,
                                                 pitch,
                                                 buffer,
                                                 &dst_rect);
    assert(result == 0);

    DISPMANX_UPDATE_HANDLE_T update = vc_dispmanx_update_start(0);
    assert(update != 0);

    VC_RECT_T src_rect;
    vc_dispmanx_rect_set(&src_rect, 0, 0, width << 16, height << 16);
    vc_dispmanx_rect_set(&dst_rect,
                         (info->width - width) / 2,
                         (info->height - height) / 2,
                         width,
                         height);

    VC_DISPMANX_ALPHA_T alpha =
    {
        DISPMANX_FLAGS_ALPHA_FIXED_ALL_PIXELS, 
        255, /*alpha 0->255*/
        0
    };

    DISPMANX_ELEMENT_HANDLE_T element =
        vc_dispmanx_element_add(update,
                                display,
                                3, // layer
                                &dst_rect,
                                resource,
                                &src_rect,
                                DISPMANX_PROTECTION_NONE,
                                &alpha,
                                NULL, // clamp
                                DISPMANX_NO_ROTATE);
    assert(element != 0);

    result = vc_dispmanx_update_submit_sync(update);
    assert(result == 0);

    sleep(10);

    update = vc_dispmanx_update_start(0);
    assert(update != 0);
    result = vc_dispmanx_element_remove(update, element);
    assert(result == 0);
    result = vc_dispmanx_update_submit_sync(update);
    assert(result == 0);

    result = vc_dispmanx_resource_delete(resource);
    assert(result == 0);
}

void
fullscreen(
    DISPMANX_DISPLAY_HANDLE_T display,
    DISPMANX_MODEINFO_T *info)
{
    int width = info->width / 2;
    int height = info->height / 2;

    VC_IMAGE_TYPE_T type = VC_IMAGE_RGBA32;
    int pitch = ALIGN_UP(width * 4, 32);
    void *buffer = calloc(1, pitch * height);

    printf("taking snapshot %dx%d\n", width, height);
    takeSnapshot(display, info, type, width, height, pitch, buffer);

    printf("displaying snapshot %dx%d\n", width, height);
    showSnapshot(display, info, type, width, height, pitch, buffer);
    free(buffer);
}

int main(void)
{
    bcm_host_init();

    DISPMANX_DISPLAY_HANDLE_T display = vc_dispmanx_display_open(0);
    assert(display != 0);

    DISPMANX_MODEINFO_T info;
    int result = vc_dispmanx_display_get_info(display, &info);
    assert(result == 0);

    fullscreen(display, &info);

    result = vc_dispmanx_display_close(display);
    assert(result == 0);

    return 0;
}