我有下面的代码——这是对这里代码的修改。在这里结合本教程。
static void * snapshot_function(void *userdata){
CustomData *data = (CustomData *) userdata;
gint width, height;
GstSample *sample;
GError *error = NULL;
GdkPixbuf *pixbuf;
gint64 duration, position;
GstStateChangeReturn ret;
gboolean res;
GstMapInfo map;
/* Build pipeline */
data->pipeline_snapshot = gst_parse_launch(pipeline_description_snapshot, &error);
if (error) {
gchar *message =
g_strdup_printf("Unable to build pipeline: %s", error->message);
g_clear_error(&error);
set_ui_message(message, data);
g_free(message);
return NULL;
}
if (error != NULL) {
g_print ("could not construct pipeline: %sn", error->message);
g_error_free (error);
exit (-1);
}
/* get sink */
data->snapshot_sink = gst_bin_get_by_name (GST_BIN (data->pipeline_snapshot), "sink");
/* set to PAUSED to make the first frame arrive in the sink */
ret = gst_element_set_state (data->pipeline_snapshot, GST_STATE_PAUSED);
switch (ret) {
case GST_STATE_CHANGE_FAILURE:
g_print ("failed to play the filen");
exit (-1);
case GST_STATE_CHANGE_NO_PREROLL:
/* for live sources, we need to set the pipeline to PLAYING before we can
* receive a buffer. We don't do that yet */
g_print ("live sources not supported yetn");
exit (-1);
default:
break;
}
/* This can block for up to 5 seconds. If your machine is really overloaded,
* it might time out before the pipeline prerolled and we generate an error. A
* better way is to run a mainloop and catch errors there. */
ret = gst_element_get_state (data->pipeline_snapshot, NULL, NULL, 5 * GST_SECOND);
if (ret == GST_STATE_CHANGE_FAILURE) {
g_print ("failed to play the filen");
exit (-1);
}
/* get the duration */
gst_element_query_duration (data->pipeline_snapshot, GST_FORMAT_TIME, &duration);
if (duration != -1)
/* we have a duration, seek to 5% */
position = duration * 5 / 100;
else
/* no duration, seek to 1 second, this could EOS */
position = 1 * GST_SECOND;
/* seek to the a position in the file. Most files have a black first frame so
* by seeking to somewhere else we have a bigger chance of getting something
* more interesting. An optimisation would be to detect black images and then
* seek a little more */
gst_element_seek_simple (data->pipeline_snapshot, GST_FORMAT_TIME,
GST_SEEK_FLAG_KEY_UNIT | GST_SEEK_FLAG_FLUSH, position);
/* get the preroll buffer from appsink, this block untils appsink really
* prerolls */
g_signal_emit_by_name (data->snapshot_sink, "pull-preroll", &sample, NULL);
gst_object_unref (data->snapshot_sink);
/* if we have a buffer now, convert it to a pixbuf. It's possible that we
* don't have a buffer because we went EOS right away or had an error. */
if (sample) {
GstBuffer *buffer;
GdkPixbuf *pixbuf;
GstCaps *caps;
GstStructure *s;
/* get the snapshot buffer format now. We set the caps on the appsink so
* that it can only be an rgb buffer. The only thing we have not specified
* on the caps is the height, which is dependent on the pixel-aspect-ratio
* of the source material */
caps = gst_sample_get_caps (sample);
if (!caps) {
g_print ("could not get snapshot formatn");
exit (-1);
}
s = gst_caps_get_structure (caps, 0);
/* we need to get the final caps on the buffer to get the size */
res = gst_structure_get_int (s, "width", &width);
res |= gst_structure_get_int (s, "height", &height);
if (!res) {
g_print ("could not get snapshot dimensionn");
exit (-1);
}
/* create pixmap from buffer and save, gstreamer video buffers have a stride
* that is rounded up to the nearest multiple of 4 */
buffer = gst_sample_get_buffer (sample);
gst_buffer_map (buffer, &map, GST_MAP_READ);
pixbuf = gdk_pixbuf_new_from_data (map.data,GDK_COLORSPACE_RGB, FALSE, 8, width, height, GST_ROUND_UP_4 (width * 3), NULL, NULL);
/* save the pixbuf */
gdk_pixbuf_save (pixbuf, "snapshot.png", "png", &error, NULL);
gst_buffer_unmap (buffer, &map);
} else {
g_print ("could not make snapshot");
}
/* cleanup and exit */
gst_element_set_state (data->pipeline_snapshot, GST_STATE_NULL);
gst_object_unref (data->pipeline_snapshot);
exit (0);
}
然而，在编译时，我得到了以下链接器错误：
C:\Users/user1/AndroidStudioProjects/Project/app/jni/tutorial-3.C:344:对`gdk_pixbuf_new_from_data'的未定义引用
C:\Users/user1/AndroidStudioProjects/Project/app/jni/tutorial-3.C:347:未定义对"gdk_pixbuf_save"clang++的引用：错误：链接器命令失败，退出代码为1(使用-v查看调用(
我的文件顶部有#include <gdk-pixbuf-2.0/gdk-pixbuf/gdk-pixbuf.h>，有人知道我可能做错了什么吗？
链接有问题，所以需要查看构建脚本，似乎忘记了链接库。例如，如果你使用cmake，它会看起来像这样：
target_link_libraries(tutorial-3 gdk_pixbuf-2.0)