Add libpng backend

src/backend_libpng.c

@@ -0,0 +1,193 @@
+#include "backend_libpng.h"
+#include "backend.h"
+#include "source.h"
+
+#include <alloca.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <png.h>
+
+struct private {
+  FILE *file;
+  png_structp png;
+  png_infop info;
+};
+
+static void source_free(struct imv_source *src)
+{
+  free(src->name);
+  src->name = NULL;
+
+  struct private *private = src->private;
+  png_destroy_read_struct(&private->png, &private->info, NULL);
+  if (private->file) {
+    fclose(private->file);
+  }
+
+  free(src->private);
+  src->private = NULL;
+
+  free(src);
+}
+
+static struct imv_bitmap *to_imv_bitmap(int width, int height, void *bitmap)
+{
+  struct imv_bitmap *bmp = malloc(sizeof(struct imv_bitmap));
+  bmp->width = width;
+  bmp->height = height;
+  bmp->format = IMV_ABGR;
+  bmp->data = bitmap;
+  return bmp;
+}
+
+static void report_error(struct imv_source *src)
+{
+  if (!src->callback) {
+    fprintf(stderr, "imv_source(%s) has no callback configured. "
+                    "Discarding error.\n", src->name);
+    return;
+  }
+
+  struct imv_source_message msg;
+  msg.source = src;
+  msg.user_data = src->user_data;
+  msg.bitmap = NULL;
+  msg.error = "Internal error";
+
+  src->callback(&msg);
+}
+
+
+static void send_bitmap(struct imv_source *src, void *bitmap)
+{
+  if (!src->callback) {
+    fprintf(stderr, "imv_source(%s) has no callback configured. "
+                    "Discarding result.\n", src->name);
+    return;
+  }
+
+  struct imv_source_message msg;
+  msg.source = src;
+  msg.user_data = src->user_data;
+  msg.bitmap = to_imv_bitmap(src->width, src->height, bitmap);
+  msg.frametime = 0;
+  msg.error = NULL;
+
+  src->callback(&msg);
+}
+
+static void load_image(struct imv_source *src)
+{
+  struct private *private = src->private;
+
+  if (setjmp(png_jmpbuf(private->png))) {
+    report_error(src);
+    return;
+  }
+
+  png_bytep *rows = alloca(sizeof(png_bytep) * src->height);
+  size_t row_len = png_get_rowbytes(private->png, private->info);
+  rows[0] = malloc(src->height * row_len);
+  for (int y = 1; y < src->height; ++y) {
+    rows[y] = rows[0] + row_len * y;
+  }
+
+  if (setjmp(png_jmpbuf(private->png))) {
+    free(rows[0]);
+    report_error(src);
+    return;
+  }
+
+  png_read_image(private->png, rows);
+  fclose(private->file);
+  private->file = NULL;
+  send_bitmap(src, rows[0]);
+}
+
+static enum backend_result open_path(const char *path, struct imv_source **src)
+{
+
+  unsigned char header[8];
+  FILE *f = fopen(path, "rb");
+  if (!f) {
+    return BACKEND_BAD_PATH;
+  }
+  fread(header, 1, sizeof header, f);
+  if (png_sig_cmp(header, 0, sizeof header)) {
+    fclose(f);
+    return BACKEND_UNSUPPORTED;
+  }
+
+  struct private *private = malloc(sizeof(struct private));
+  private->file = f;
+  private->png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+  if (!private->png) {
+    fclose(private->file);
+    free(private);
+    return BACKEND_UNSUPPORTED;
+  }
+
+  private->info = png_create_info_struct(private->png);
+  if (!private->info) {
+    png_destroy_read_struct(&private->png, NULL, NULL);
+    fclose(private->file);
+    free(private);
+    return BACKEND_UNSUPPORTED;
+  }
+
+  if (setjmp(png_jmpbuf(private->png))) {
+    png_destroy_read_struct(&private->png, &private->info, NULL);
+    fclose(private->file);
+    free(private);
+    return BACKEND_UNSUPPORTED;
+  }
+
+  png_init_io(private->png, private->file);
+  png_set_sig_bytes(private->png, sizeof header);
+  png_read_info(private->png, private->info);
+
+  png_set_gray_to_rgb(private->png);
+
+  png_read_update_info(private->png, private->info);
+
+  struct imv_source *source = calloc(1, sizeof(struct imv_source));
+  source->name = strdup(path);
+  if (setjmp(png_jmpbuf(private->png))) {
+    free(source->name);
+    free(source);
+    png_destroy_read_struct(&private->png, &private->info, NULL);
+    fclose(private->file);
+    free(private);
+    return BACKEND_UNSUPPORTED;
+  }
+
+  source->width = png_get_image_width(private->png, private->info);
+  source->height = png_get_image_height(private->png, private->info);
+  source->num_frames = 1;
+  source->next_frame = 1;
+  source->load_first_frame = &load_image;
+  source->load_next_frame = NULL;
+  source->free = &source_free;
+  source->callback = NULL;
+  source->user_data = NULL;
+  source->private = private;
+
+  *src = source;
+  return BACKEND_SUCCESS;
+}
+
+static void backend_free(struct imv_backend *backend)
+{
+  free(backend);
+}
+
+struct imv_backend *imv_backend_libpng(void)
+{
+  struct imv_backend *backend = malloc(sizeof(struct imv_backend));
+  backend->name = "libpng (libpng/zlib license)";
+  backend->open_path = &open_path;
+  backend->free = &backend_free;
+  return backend;
+}

src/backend_libpng.h

@@ -0,0 +1,9 @@
+#ifndef IMV_BACKEND_LIBPNG_H
+#define IMV_BACKEND_LIBPNG_H
+
+struct imv_backend;
+
+/* Create an instance of the libpng backend */
+struct imv_backend *imv_backend_libpng(void);
+
+#endif