Examples/spi_master: spiffier graphics

examples/peripherals/spi_master/main/pretty_effect.c

@@ -0,0 +1,61 @@
+/*
+   This code generates an effect that should pass the 'fancy graphics' qualification
+   as set in the comment in the spi_master code.
+
+   This example code is in the Public Domain (or CC0 licensed, at your option.)
+
+   Unless required by applicable law or agreed to in writing, this
+   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+   CONDITIONS OF ANY KIND, either express or implied.
+*/
+
+#include <math.h>
+#include "pretty_effect.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() 
+{
+    return decode_image(&pixels);
+}