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Grayscale quantization and fixing some defaults to support rgb565

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Patedam
2026-03-15 22:01:45 -04:00
parent 7f296f9857
commit 2c79be36ef
5 changed files with 368 additions and 288 deletions
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208
Provider/main/api/display/image.cpp
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@@ -1,113 +1,145 @@
#include "../../lv_setup.hpp"
#include "../../lodepng/lodepng.h"
#include "../../lodepng_alloc.hpp"
#include "../../lv_setup.hpp"
#include "esp_heap_caps.h"
#include "esp_http_server.h"
#include "esp_log.h"
#include "esp_heap_caps.h"
#include "esp_random.h"
#include "lvgl.h"
#include <string.h>
#include "../../lodepng_alloc.hpp"
internal const char *kTagDisplayImage = "API_DISPLAY_IMAGE";
internal esp_err_t api_display_image_handler(httpd_req_t *req)
{
httpd_resp_set_hdr(req, "Access-Control-Allow-Origin", "*");
// We are generating PNG on the fly, don't let it be cached locally immediately
httpd_resp_set_hdr(req, "Cache-Control", "no-cache, no-store, must-revalidate");
httpd_resp_set_type(req, "image/png");
httpd_resp_set_hdr(req, "Access-Control-Allow-Origin", "*");
if (xSemaphoreTake(g_LvglMutex, pdMS_TO_TICKS(5000)) != pdTRUE)
{
ESP_LOGE(kTagDisplayImage, "Failed to get LVGL mutex");
httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "LVGL busy");
return ESP_FAIL;
}
// We are generating PNG on the fly, don't let it be cached locally
// immediately
httpd_resp_set_hdr(req, "Cache-Control",
"no-cache, no-store, must-revalidate");
httpd_resp_set_type(req, "image/png");
// Change the background color securely to a random grayscale value
// esp_random() returns 32 bits, we just take the lowest 8.
uint8_t rand_gray = esp_random() & 0xFF;
lv_obj_t* active_screen = lv_screen_active();
lv_obj_set_style_bg_color(active_screen, lv_color_make(rand_gray, rand_gray, rand_gray), LV_PART_MAIN);
if (xSemaphoreTake(g_LvglMutex, pdMS_TO_TICKS(5000)) != pdTRUE)
{
ESP_LOGE(kTagDisplayImage, "Failed to get LVGL mutex");
httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "LVGL busy");
return ESP_FAIL;
}
// Force a screen refresh to get the latest rendered frame
lv_refr_now(g_LvglDisplay);
// Change the background color securely to a random grayscale value
// esp_random() returns 32 bits, we just take the lowest 8.
uint8_t rand_gray = esp_random() & 0xFF;
lv_obj_t *active_screen = lv_screen_active();
// lv_obj_set_style_bg_color(active_screen, lv_color_make(rand_gray,
// rand_gray, rand_gray), LV_PART_MAIN);
lv_draw_buf_t *draw_buf = lv_display_get_buf_active(g_LvglDisplay);
if (!draw_buf)
{
xSemaphoreGive(g_LvglMutex);
ESP_LOGE(kTagDisplayImage, "No active draw buffer available");
httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "Display uninitialized");
return ESP_FAIL;
}
uint32_t width = CONFIG_CALENDINK_DISPLAY_WIDTH;
uint32_t height = CONFIG_CALENDINK_DISPLAY_HEIGHT;
// LodePNG expects tightly packed data without stride padding.
// Ensure we copy the data if stride differs from width.
uint8_t *packed_data = (uint8_t *)draw_buf->data;
bool needs_free = false;
if (draw_buf->header.stride != width)
{
ESP_LOGI(kTagDisplayImage, "Stride %lu differs from width %lu. Repacking buffer...", draw_buf->header.stride, width);
packed_data = (uint8_t *)heap_caps_malloc(width * height, MALLOC_CAP_SPIRAM);
if (!packed_data)
{
xSemaphoreGive(g_LvglMutex);
ESP_LOGE(kTagDisplayImage, "Failed to allocate packed buffer in PSRAM");
httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "Out of memory");
return ESP_FAIL;
}
needs_free = true;
for (uint32_t y = 0; y < height; ++y)
{
memcpy(packed_data + (y * width), (uint8_t *)draw_buf->data + (y * draw_buf->header.stride), width);
}
}
// Convert LVGL 8-bit L8 buffer to 8-bit grayscale PNG using LodePNG.
// LCT_GREY = 0, bitdepth = 8
unsigned char *png = nullptr;
size_t pngsize = 0;
// We are about to start a huge memory operation inside LodePNG.
// We reset our 2MB PSRAM bump allocator to 0 bytes used.
lodepng_allocator_reset();
ESP_LOGI(kTagDisplayImage, "Encoding %lux%lu frame to PNG...", width, height);
unsigned error = lodepng_encode_memory(&png, &pngsize, packed_data, width, height, LCT_GREY, 8);
if (needs_free)
{
free(packed_data);
}
// Force a screen refresh to get the latest rendered frame
lv_refr_now(g_LvglDisplay);
lv_draw_buf_t *draw_buf = lv_display_get_buf_active(g_LvglDisplay);
if (!draw_buf)
{
xSemaphoreGive(g_LvglMutex);
ESP_LOGE(kTagDisplayImage, "No active draw buffer available");
httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR,
"Display uninitialized");
return ESP_FAIL;
}
if (error)
uint32_t width = CONFIG_CALENDINK_DISPLAY_WIDTH;
uint32_t height = CONFIG_CALENDINK_DISPLAY_HEIGHT;
// We allocate a new buffer for the tightly packed 8-bit PNG grayscale data.
// Converting RGB565 frame to 4-level grayscale (quantized to 0, 85, 170, 255).
uint8_t *packed_data =
(uint8_t *)heap_caps_malloc(width * height, MALLOC_CAP_SPIRAM);
if (!packed_data)
{
packed_data = (uint8_t *)malloc(width * height); // Fallback
if (!packed_data)
{
ESP_LOGE(kTagDisplayImage, "PNG encoding error %u: %s", error, lodepng_error_text(error));
httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "PNG generation failed");
return ESP_FAIL;
xSemaphoreGive(g_LvglMutex);
ESP_LOGE(kTagDisplayImage, "Failed to allocate packed buffer");
httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR,
"Out of memory");
return ESP_FAIL;
}
}
ESP_LOGI(kTagDisplayImage, "Prepared PNG, size: %zu bytes. Sending to client...", pngsize);
esp_err_t res = httpd_resp_send(req, (const char *)png, pngsize);
// LVGL renders into RGB565 (2 bytes per pixel).
// Iterating to create an 8-bit grayscale PNG using 4 specific values.
for (uint32_t y = 0; y < height; ++y)
{
const uint16_t *src_row =
(const uint16_t *)((const uint8_t *)draw_buf->data +
(y * draw_buf->header.stride));
uint8_t *dst_row = packed_data + (y * width);
// No need to free(png) because it is managed by our bump allocator
// which automatically resets the entire 2MB buffer to 0 next time
// lodepng_allocator_reset() is called.
for (uint32_t x = 0; x < width; ++x)
{
uint16_t c = src_row[x];
// Note: LVGL may use swapped bytes for SPI rendering depending on config,
// but in memory RGB565 is standard if no SWAP is active. Usually standard
// RGB565 format: R(5) G(6) B(5)
uint8_t r_5 = (c >> 11) & 0x1F;
uint8_t g_6 = (c >> 5) & 0x3F;
uint8_t b_5 = c & 0x1F;
return res;
// Expand to 8 bits
uint8_t r = (r_5 << 3) | (r_5 >> 2);
uint8_t g = (g_6 << 2) | (g_6 >> 4);
uint8_t b = (b_5 << 3) | (b_5 >> 2);
// Simple luminance calculation (fast)
uint8_t lum = (r * 77 + g * 150 + b * 29) >> 8;
// Quantize to 4 levels (0..3)
uint8_t level = lum >> 6;
// Expand level back to 8-bit for PNG: 0, 85, 170, 255
dst_row[x] = level * 85;
}
}
// Convert LVGL 8-bit L8 buffer to 8-bit grayscale PNG using LodePNG.
// LCT_GREY = 0, bitdepth = 8
unsigned char *png = nullptr;
size_t pngsize = 0;
// We are about to start a huge memory operation inside LodePNG.
// We reset our 3MB PSRAM bump allocator to 0 bytes used.
lodepng_allocator_reset();
ESP_LOGI(kTagDisplayImage, "Encoding %lux%lu frame to PNG...", width, height);
unsigned error = lodepng_encode_memory(&png, &pngsize, packed_data, width,
height, LCT_GREY, 8);
free(packed_data);
xSemaphoreGive(g_LvglMutex);
if (error)
{
ESP_LOGE(kTagDisplayImage, "PNG encoding error %u: %s", error,
lodepng_error_text(error));
httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR,
"PNG generation failed");
return ESP_FAIL;
}
ESP_LOGI(kTagDisplayImage,
"Prepared PNG, size: %zu bytes. Sending to client...", pngsize);
esp_err_t res = httpd_resp_send(req, (const char *)png, pngsize);
// No need to free(png) because it is managed by our bump allocator
// which automatically resets the entire 2MB buffer to 0 next time
// lodepng_allocator_reset() is called.
return res;
}
httpd_uri_t api_display_image_uri = {
.uri = "/api/display/image.png",
.method = HTTP_GET,
.handler = api_display_image_handler,
.user_ctx = NULL};
httpd_uri_t api_display_image_uri = {.uri = "/api/display/image.png",
.method = HTTP_GET,
.handler = api_display_image_handler,
.user_ctx = NULL};