From b947448795d604f169246b0c3191028ae6a0ab83 Mon Sep 17 00:00:00 2001
From: Daniel Eklöf <daniel@ekloef.se>
Date: Sat, 1 Aug 2020 15:32:48 +0200
Subject: Initial commit

Can display a single PNG image scaled-to-fit on all outputs.
---
 png.c | 143 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 143 insertions(+)
 create mode 100644 png.c

(limited to 'png.c')

diff --git a/png.c b/png.c
new file mode 100644
index 0000000..7dd4276
--- /dev/null
+++ b/png.c
@@ -0,0 +1,143 @@
+#include "png-wbg.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
+#include <assert.h>
+
+#include <png.h>
+#include <pixman.h>
+
+#define LOG_MODULE "png"
+#define LOG_ENABLE_DBG 0
+#include "log.h"
+#include "stride.h"
+
+pixman_image_t *
+png_load(const char *path)
+{
+    pixman_image_t *pix = NULL;
+
+    FILE *fp = NULL;
+    png_structp png_ptr = NULL;
+    png_infop info_ptr = NULL;
+    png_bytepp row_pointers = NULL;
+    uint8_t *image_data = NULL;
+
+    /* open file and test for it being a png */
+    if ((fp = fopen(path, "rb")) == NULL) {
+        //LOG_ERRNO("%s: failed to open", path);
+        goto err;
+    }
+
+    /* Verify PNG header */
+    uint8_t header[8] = {0};
+    if (fread(header, 1, 8, fp) != 8 || png_sig_cmp(header, 0, 8)) {
+        // LOG_ERR("%s: not a PNG", path);
+        goto err;
+    }
+
+    /* Prepare for reading the PNG */
+    if ((png_ptr = png_create_read_struct(
+             PNG_LIBPNG_VER_STRING, NULL, NULL, NULL)) == NULL ||
+        (info_ptr = png_create_info_struct(png_ptr)) == NULL)
+    {
+        LOG_ERR("%s: failed to initialize libpng", path);
+        goto err;
+    }
+
+    if (setjmp(png_jmpbuf(png_ptr))) {
+        LOG_ERR("%s: libpng error", path);
+        goto err;
+    }
+
+    png_init_io(png_ptr, fp);
+    png_set_sig_bytes(png_ptr, 8);
+
+    /* Get meta data */
+    png_read_info(png_ptr, info_ptr);
+    int width = png_get_image_width(png_ptr, info_ptr);
+    int height = png_get_image_height(png_ptr, info_ptr);
+    png_byte color_type = png_get_color_type(png_ptr, info_ptr);
+    png_byte bit_depth __attribute__((unused)) = png_get_bit_depth(png_ptr, info_ptr);
+    int channels __attribute__((unused)) = png_get_channels(png_ptr, info_ptr);
+
+    LOG_DBG("%s: %dx%d@%hhubpp, %d channels", path, width, height, bit_depth, channels);
+
+    png_set_packing(png_ptr);
+    png_set_interlace_handling(png_ptr);
+    png_set_strip_16(png_ptr);  /* "pack" 16-bit colors to 8-bit */
+    png_set_bgr(png_ptr);
+
+    /* pixman expects pre-multiplied alpha */
+    png_set_alpha_mode(png_ptr, PNG_ALPHA_PREMULTIPLIED, 1.0);
+
+    /* Tell libpng to expand to RGB(A) when necessary, and tell pixman
+     * whether we have alpha or not */
+    pixman_format_code_t format;
+    switch (color_type) {
+    case PNG_COLOR_TYPE_GRAY:
+    case PNG_COLOR_TYPE_GRAY_ALPHA:
+        LOG_DBG("%d-bit gray%s", bit_depth,
+                color_type == PNG_COLOR_TYPE_GRAY_ALPHA ? "+alpha" : "");
+
+        if (bit_depth < 8)
+            png_set_expand_gray_1_2_4_to_8(png_ptr);
+
+        png_set_gray_to_rgb(png_ptr);
+        format = color_type == PNG_COLOR_TYPE_GRAY ? PIXMAN_r8g8b8 : PIXMAN_a8r8g8b8;
+        break;
+
+    case PNG_COLOR_TYPE_PALETTE:
+        LOG_DBG("%d-bit colormap%s", bit_depth,
+                png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS) ? "+tRNS" : "");
+
+        png_set_palette_to_rgb(png_ptr);
+        if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
+            png_set_tRNS_to_alpha(png_ptr);
+            format = PIXMAN_a8r8g8b8;
+        } else
+            format = PIXMAN_r8g8b8;
+        break;
+
+    case PNG_COLOR_TYPE_RGB:
+        LOG_DBG("RGB");
+        format = PIXMAN_r8g8b8;
+        break;
+
+    case PNG_COLOR_TYPE_RGBA:
+        LOG_DBG("RGBA");
+        format = PIXMAN_a8r8g8b8;
+        break;
+    }
+
+    png_read_update_info(png_ptr, info_ptr);
+
+    size_t row_bytes __attribute__((unused)) = png_get_rowbytes(png_ptr, info_ptr);
+    int stride = stride_for_format_and_width(format, width);
+    image_data = malloc(height * stride);
+
+    LOG_DBG("stride=%d, row-bytes=%zu", stride, row_bytes);
+    assert(stride >= row_bytes);
+
+    row_pointers = malloc(height * sizeof(png_bytep));
+    for (int i = 0; i < height; i++)
+        row_pointers[i] = &image_data[i * stride];
+
+    png_read_image(png_ptr, row_pointers);
+
+    pix = pixman_image_create_bits_no_clear(
+        format, width, height, (uint32_t *)image_data, stride);
+
+err:
+    if (pix == NULL)
+        free(image_data);
+    free(row_pointers);
+    if (png_ptr != NULL)
+        png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+    if (fp != NULL)
+        fclose(fp);
+
+    return pix;
+}
-- 
cgit v1.2.3