QR masks

1 files changed, 46 insertions, 0 deletions

diff --git a/lpg/libqr/qr-mask.c b/lpg/libqr/qr-mask.c
new file mode 100644
index 0000000..2a63c0b
--- /dev/null
+++ b/lpg/libqr/qr-mask.c
@@ -0,0 +1,46 @@
+#include <limits.h>
+#include <stdlib.h>
+#include "qr-bitmap.h"
+#include "qr-mask.h"
+
+struct qr_bitmap * qr_mask_apply(const struct qr_bitmap * orig,
+                                 unsigned int mask)
+{
+        struct qr_bitmap * bmp;
+        int i, j;
+
+        if (mask & ~0x7)
+                return 0;
+
+        bmp = qr_bitmap_clone(orig);
+        if (!bmp)
+                return 0;
+
+        /* Slow version for now; we can optimize later */
+
+        for (i = 0; i < bmp->height; ++i) {
+                unsigned char * p = bmp->bits + i * bmp->stride;
+
+                for (j = 0; j < bmp->width; ++j) {
+                        int bit = j % CHAR_BIT;
+                        size_t off = j / CHAR_BIT;
+                        int t;
+
+                        switch (mask) {
+                        case 0: t = (i + j) % 2; break;
+                        case 1: t = i % 2; break;
+                        case 2: t = j % 3; break;
+                        case 3: t = (i + j) % 3; break;
+                        case 4: t = (i/2 + j/3) % 2; break;
+                        case 5: t = ((i*j) % 2) + ((i*j) % 3); break;
+                        case 6: t = (((i*j) % 2) + ((i*j) % 3)) % 2; break;
+                        case 7: t = (((i*j) % 3) + ((i+j) % 2)) % 2; break;
+                        }
+
+                        p[off] ^= (t == 0) << bit;
+                }
+        }
+
+        return bmp;
+}
+