lavfi/opencl: add ff_opencl_print_const_matrix_3x3()

This is used to print a 3x3 matrix into a part of OpenCL
source code.
Signed-off-by: Ruiling Song <ruiling.song@intel.com>

libavfilter/opencl.c

@@ -337,3 +337,16 @@ int ff_opencl_filter_work_size_from_image(AVFilterContext *avctx,
 
     return 0;
 }
+
+void ff_opencl_print_const_matrix_3x3(AVBPrint *buf, const char *name_str,
+                                      double mat[3][3])
+{
+    int i, j;
+    av_bprintf(buf, "__constant float %s[9] = {\n", name_str);
+    for (i = 0; i < 3; i++) {
+        for (j = 0; j < 3; j++)
+            av_bprintf(buf, " %.5ff,", mat[i][j]);
+        av_bprintf(buf, "\n");
+    }
+    av_bprintf(buf, "};\n");
+}

libavfilter/opencl.h

@@ -25,6 +25,7 @@
 // it was introduced in OpenCL 2.0.
 #define CL_USE_DEPRECATED_OPENCL_1_2_APIS
 
+#include "libavutil/bprint.h"
 #include "libavutil/buffer.h"
 #include "libavutil/hwcontext.h"
 #include "libavutil/hwcontext_opencl.h"
@@ -124,5 +125,12 @@ int ff_opencl_filter_work_size_from_image(AVFilterContext *avctx,
                                           size_t *work_size,
                                           AVFrame *frame, int plane,
                                           int block_alignment);
+/**
+ * Print a 3x3 matrix into a buffer as __constant array, which could
+ * be included in an OpenCL program.
+*/
+
+void ff_opencl_print_const_matrix_3x3(AVBPrint *buf, const char *name_str,
+                                      double mat[3][3]);
 
 #endif /* AVFILTER_OPENCL_H */