QR masks

5 files changed, 78 insertions, 0 deletions

diff --git a/lpg/libqr/Makefile b/lpg/libqr/Makefile
index 49f89d4..5eba18b 100644
--- a/lpg/libqr/Makefile
+++ b/lpg/libqr/Makefile
@@ -9,6 +9,7 @@ OBJECTS :=      code-common.o           \
                 qr-bitmap-pbm.o         \
                 qr-bitmap-render.o      \
                 qr-bitstream.o          \
+                qr-mask.o               \
                 rs-encode.o
 
 CFLAGS := -std=c89 -pedantic -I. -Wall
diff --git a/lpg/libqr/qr-bitmap.c b/lpg/libqr/qr-bitmap.c
index e42b550..1a5ca52 100644
--- a/lpg/libqr/qr-bitmap.c
+++ b/lpg/libqr/qr-bitmap.c
@@ -48,6 +48,25 @@ void qr_bitmap_destroy(struct qr_bitmap * bmp)
         }
 }
 
+struct qr_bitmap * qr_bitmap_clone(const struct qr_bitmap * src)
+{
+        struct qr_bitmap * bmp;
+        size_t size;
+
+        bmp = qr_bitmap_create(src->width, src->height, !!src->mask);
+        if (!bmp)
+                return 0;
+
+        assert(bmp->stride == src->stride);
+
+        size = bmp->width * bmp->stride;
+        memcpy(bmp->bits, src->bits, size);
+        if (bmp->mask)
+                memcpy(bmp->mask, src->mask, size);
+
+        return bmp;
+}
+
 void qr_bitmap_merge(struct qr_bitmap * dest, const struct qr_bitmap * src)
 {
         unsigned char * d, * s, * m;
diff --git a/lpg/libqr/qr-bitmap.h b/lpg/libqr/qr-bitmap.h
index d60049a..936b23d 100644
--- a/lpg/libqr/qr-bitmap.h
+++ b/lpg/libqr/qr-bitmap.h
@@ -11,6 +11,8 @@ struct qr_bitmap {
 struct qr_bitmap * qr_bitmap_create(int width, int height, int masked);
 void qr_bitmap_destroy(struct qr_bitmap *);
 
+struct qr_bitmap * qr_bitmap_clone(const struct qr_bitmap *);
+
 void qr_bitmap_merge(struct qr_bitmap * dest, const struct qr_bitmap * src);
 
 void qr_bitmap_render(const struct qr_bitmap * bmp,
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;
+}
+
diff --git a/lpg/libqr/qr-mask.h b/lpg/libqr/qr-mask.h
new file mode 100644
index 0000000..b3f3523
--- /dev/null
+++ b/lpg/libqr/qr-mask.h
@@ -0,0 +1,10 @@
+#ifndef QR_MASK_H
+#define QR_MASK_H
+
+#include "qr-bitmap.h"
+
+struct qr_bitmap * qr_mask_apply(const struct qr_bitmap * orig,
+                                 unsigned int mask);
+
+#endif
+