Adding my Bitmap2Path sample for 1on1 meeting.

samplecode/SampleBitmap2Path.cpp

+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SampleCode.h"
+#include "SkView.h"
+#include "SkCanvas.h"
+#include "SkPathOps.h"
+
+#define SQRT_2 1.41421356237f
+typedef void (*line2path)(SkPath*, const char*, int, int);
+
+static int getBit( const char *buffer, int x ) {
+    int byte = x >> 8;
+    int bit = x & 7;
+
+    return buffer[byte] & (1 << bit);
+}
+
+static void line2path_pixel(SkPath* path, const char* line,
+                            int lineIdx, int width) {
+    for (int i = 0; i < width; ++i) {
+        // simply makes every ON pixel into a rect path
+        if (getBit(line,i)) {                       
+            path->addRect(SkRect::MakeXYWH(i, lineIdx, 1, 1),
+                          SkPath::kCW_Direction);
+        }
+    }
+}
+
+static void line2path_pixelCircle(SkPath* path, const char* line,
+                                  int lineIdx, int width) {
+    for (int i = 0; i < width; ++i) {
+        // simply makes every ON pixel into a circle path
+        if (getBit(line,i)) {                       
+            path->addCircle(i + SkFloatToScalar(0.5f),
+                            lineIdx + SkFloatToScalar(0.5f),
+                            SkFloatToScalar(SQRT_2 / 2.0f));
+            /* I'm shifting the center of the circles by half a pixel
+             * (to align with corresponding rectangular pixels)
+             * Should I instead be shifting the rect pixels such that
+             * their path centers are consistent with the original bitmap
+             * pixels?
+             */
+        }
+    }
+}
+
+static void line2path_span(SkPath* path, const char* line,
+                           int lineIdx, int width) {
+    bool state = 0;

[reed1, 2013/06/14 18:59:39]

does state mean "inside a run of pixels"?

+    int start = 1;
+
+    for (int i = 0; i < width; ++i) {
+        if (i==width-1) { // if the end of a scanline, close open paths

[reed1, 2013/06/14 18:59:39]

rather than check for this every time through the loop, why not just fall
through to this code after the loop (i < width - 1) terminates?

+            if (state==1) {
+                int end = 0;
+                if (getBit(line,i)) ++end;
+                path->addRect(SkRect::MakeXYWH(start, lineIdx,
+                                               i + end - start, 1),
+                              SkPath::kCW_Direction);
+            } else if (getBit(line,i)) {
+                path->addRect(SkRect::MakeXYWH(i, lineIdx, 1, 1),
+                              SkPath::kCW_Direction);
+            }
+            state = 0;
+        }else if ( (getBit(line,i)!=0) != state ) { // if transition

[reed1, 2013/06/14 18:59:39]

yick -- we're calling getBit more than once per-bit. Can we just assign it to a
local var, and then perform the logic ?

+            if (getBit(line,i)) { // if transition on
+                state = 1; //mark beginning of span
+                start = i;
+            }else { // if transition off
+                state = 0;
+                path->addRect(SkRect::MakeXYWH(start, lineIdx, i-start, 1),
+                              SkPath::kCW_Direction);
+            }
+        }
+    }
+}
+
+static void bitmap2path(SkPath* path,
+                        const char* bitmap,
+                        const line2path l2p_fn,
+                        int h, int w, int stride) {
+// loop for every line in bitmap
+    for (int i = 0; i < h; ++i) {
+        // fn ptr handles each line separately
+        l2p_fn(path, &bitmap[i*stride], i, w);
+    }        
+}
+
+
+class Bitmap2Path : public SampleView {
+public:
+    Bitmap2Path() {
+    }
+
+protected:
+    // overrides from SkEventSink
+    virtual bool onQuery(SkEvent* evt) {
+        if (SampleCode::TitleQ(*evt)) {
+            SampleCode::TitleR(evt, "Bitmap2Path");
+            return true;
+        }
+        return this->INHERITED::onQuery(evt);
+    }
+
+    virtual void onDrawContent(SkCanvas* canvas) {
+        char raw_bits[] = {
+            0x99, 0x00, 
+            0x5a, 0x00, 
+            0x3c, 0x00, 
+            0x18, 0x00,
+            0x99, 0x00, 
+            0x5a, 0x00, 
+            0x3c, 0x00, 
+            0x18, 0x00,
+        };
+
+        // pointer into memory for binary bitmap
+        const char* bitmap = (char*) &raw_bits;
+        int h=8, w=8, str=2;
+
+        // array of funtion pointers for modes (allows looping)
+        const int numModes = 3;
+        const line2path l2p_fns[numModes] = {line2path_pixel,
+                                             line2path_pixelCircle,
+                                             line2path_span};
+        
+        // select paint for drawing binary pixels -- BLACK
+        SkPaint paint;
+        paint.setAntiAlias(true);
+        paint.setStyle(SkPaint::kFill_Style);
+        paint.setColor(SK_ColorBLACK);
+
+        // for each mode
+        for (int i = 0; i < numModes; ++i) {
+            //convert bitmap to path
+            SkPath path, simple;
+
+            // generate and simplify path
+            bitmap2path(&path, bitmap, l2p_fns[i], h, w, str);
+            Simplify(path, &simple);
+
+            //draw to canvas
+            canvas->save();
+            canvas->scale(10, 10);
+            canvas->translate(i * 10, 0);
+            canvas->drawPath(simple, paint);
+            canvas->restore();
+        }
+    }
+
+private:
+    typedef SkView INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static SkView* MyFactory() { return new Bitmap2Path; }
+static SkViewRegister reg(MyFactory);