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#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(FILE *fp, const char *path)
{
pixman_image_t *pix = NULL;
png_structp png_ptr = NULL;
png_infop info_ptr = NULL;
png_bytepp row_pointers = NULL;
uint8_t *image_data = NULL;
if (fseek(fp, 0, SEEK_SET) < 0) {
LOG_ERRNO("%s: failed to seek to beginning of file", path);
return NULL;
}
/* Verify PNG header */
uint8_t header[8] = {0};
if (fread(header, 1, 8, fp) != 8 || png_sig_cmp(header, 0, 8)) {
LOG_DBG("%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);
/* 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_x8r8g8b8;
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_x8r8g8b8;
} 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_x8r8g8b8;
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);
/* pixman expects pre-multiplied alpha */
if (format == PIXMAN_x8r8g8b8) {
for (int i = 0; i < height; i++) {
uint32_t *p = (uint32_t *)row_pointers[i];
for (int j = 0; j < width; j++, p++) {
uint8_t a = (*p >> 24) & 0xff;
uint8_t r = (*p >> 16) & 0xff;
uint8_t g = (*p >> 8) & 0xff;
uint8_t b = (*p >> 0) & 0xff;
if (a == 0xff)
continue;
if (a == 0) {
r = g = b = 0;
} else {
r = r * a / 0xff;
g = g * a / 0xff;
b = b * a / 0xff;
}
*p = (uint32_t)a << 24 | r << 16 | g << 8 | b;
}
}
}
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);
return pix;
}
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