Pipette and "On Preview Widgets" branch. See issue 227

The pipette part is already working quite nice but need to be finished. The widgets part needs more work...

rtengine/jpeg.h

@@ -0,0 +1,35 @@
+#ifndef _RT_JPEG_H
+#define _RT_JPEG_H
+
+#include <csetjmp>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <jpeglib.h>
+
+extern GLOBAL(struct jpeg_error_mgr *)
+my_jpeg_std_error (struct jpeg_error_mgr * err);
+
+extern GLOBAL(void)
+my_jpeg_stdio_src (j_decompress_ptr cinfo, FILE * infile);
+
+GLOBAL(void)
+jpeg_memory_src (j_decompress_ptr cinfo, const JOCTET * buffer, size_t bufsize);
+
+/** 
+ * @brief jpeg from file and memory use this as base to managers
+ */
+typedef struct 
+{
+    struct jpeg_source_mgr pub; /* public fields */
+    jmp_buf error_jmp_buf;      /* error handler for this instance */
+} rt_jpeg_error_mgr;
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif