twin_jpeg: add a query function to get image details from file

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

2 files changed, 66 insertions, 0 deletions

diff --git a/libtwin/twin_jpeg.c b/libtwin/twin_jpeg.c
index 273dbf7..4ddc274 100644
--- a/libtwin/twin_jpeg.c
+++ b/libtwin/twin_jpeg.c
@@ -167,3 +167,51 @@ twin_pixmap_t *twin_jpeg_to_pixmap(const char *filepath, twin_format_t fmt)
 	return pix;
 }
 
+
+twin_bool_t twin_jpeg_query(const char		*filepath,
+			    twin_coord_t	*out_width,
+			    twin_coord_t	*out_height,
+			    int			*out_components,
+			    twin_jpeg_cspace_t	*out_colorspace)
+{
+	struct jpeg_decompress_struct	cinfo;
+	struct twin_jpeg_err_mgr	jerr;
+	FILE				*infile;
+
+	/* Open file first, as example */
+	infile = fopen(filepath, "rb");
+	if (infile == NULL) {
+		fprintf(stderr, "can't open %s\n", filepath);
+		return TWIN_FALSE;
+	}
+
+	/* Error handling crap */
+	memset(&cinfo, 0, sizeof(cinfo));
+	cinfo.err = jpeg_std_error(&jerr.mgr);
+	jerr.mgr.error_exit = twin_jpeg_error_exit;
+	if (setjmp(jerr.jbuf)) {
+		jpeg_destroy_decompress(&cinfo);
+		fclose(infile);
+		return TWIN_FALSE;
+	}
+
+	/* Init libjpeg, hook it up to file and read header */
+	jpeg_create_decompress(&cinfo);
+	jpeg_stdio_src(&cinfo, infile);
+	(void)jpeg_read_header(&cinfo, TRUE);
+
+	/* Gather infos */
+	if (out_width)
+		*out_width	= cinfo.image_width;
+	if (out_height)
+		*out_height	= cinfo.image_height;
+	if (out_components)
+		*out_components	= cinfo.num_components;
+	if (out_colorspace)
+		*out_colorspace	= (twin_jpeg_cspace_t)cinfo.jpeg_color_space;
+
+	jpeg_destroy_decompress(&cinfo);
+	fclose(infile);
+
+	return TWIN_TRUE;
+}
diff --git a/libtwin/twin_jpeg.h b/libtwin/twin_jpeg.h
index 828e361..1af84db 100644
--- a/libtwin/twin_jpeg.h
+++ b/libtwin/twin_jpeg.h
@@ -23,6 +23,24 @@
 
 #include <libtwin/twin.h>
 
+/* This matches the libjpeg colorspace definitions so you don't have
+ * to use libjpeg headers in your application
+ */
+typedef enum {
+	TWIN_JCS_UNKNOWN,	/* error/unspecified */
+	TWIN_JCS_GRAYSCALE,	/* monochrome */
+	TWIN_JCS_RGB,		/* red/green/blue */
+	TWIN_JCS_YCbCr,		/* Y/Cb/Cr (also known as YUV) */
+	TWIN_JCS_CMYK,		/* C/M/Y/K */
+	TWIN_JCS_YCCK		/* Y/Cb/Cr/K */
+} twin_jpeg_cspace_t;
+
+twin_bool_t twin_jpeg_query(const char		*filepath,
+			    twin_coord_t	*out_width,
+			    twin_coord_t	*out_height,
+			    int			*out_components,
+			    twin_jpeg_cspace_t	*out_colorspace);
+
 twin_pixmap_t *twin_jpeg_to_pixmap(const char *filepath, twin_format_t fmt);
 
 #endif /* _TWIN_JPEG_H_ */