esp-idf/examples/peripherals/lcd/tjpgd/main/pretty_effect.c

/*
 * SPDX-FileCopyrightText: 2022 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: CC0-1.0
 */

#include <math.h>
#include "pretty_effect.h"
#include "sdkconfig.h"
#include "decode_image.h"

uint16_t **pixels;

//Grab a rgb16 pixel from the esp32_tiles image
static inline uint16_t get_bgnd_pixel(int x, int y)
{
    //Image has an 8x8 pixel margin, so we can also resolve e.g. [-3, 243]
    x+=8;
    y+=8;
    return pixels[y][x];
}

//This variable is used to detect the next frame.
static int prev_frame=-1;

//Instead of calculating the offsets for each pixel we grab, we pre-calculate the valueswhenever a frame changes, then re-use
//these as we go through all the pixels in the frame. This is much, much faster.
static int8_t xofs[320], yofs[240];
static int8_t xcomp[320], ycomp[240];

//Calculate the pixel data for a set of lines (with implied line size of 320). Pixels go in dest, line is the Y-coordinate of the
//first line to be calculated, linect is the amount of lines to calculate. Frame increases by one every time the entire image
//is displayed; this is used to go to the next frame of animation.
void pretty_effect_calc_lines(uint16_t *dest, int line, int frame, int linect)
{
    if (frame!=prev_frame) {
        //We need to calculate a new set of offset coefficients. Take some random sines as offsets to make everything
        //look pretty and fluid-y.
        for (int x=0; x<320; x++) xofs[x]=sin(frame*0.15+x*0.06)*4;
        for (int y=0; y<240; y++) yofs[y]=sin(frame*0.1+y*0.05)*4;
        for (int x=0; x<320; x++) xcomp[x]=sin(frame*0.11+x*0.12)*4;
        for (int y=0; y<240; y++) ycomp[y]=sin(frame*0.07+y*0.15)*4;
        prev_frame=frame;
    }
    for (int y=line; y<line+linect; y++) {
        for (int x=0; x<320; x++) {
            *dest++=get_bgnd_pixel(x+yofs[y]+xcomp[x], y+xofs[x]+ycomp[y]);
        }
    }
}


esp_err_t pretty_effect_init(void)
{
    return decode_image(&pixels);
}