Adding my Bitmap2Path sample for 1on1 meeting.

samplecode/SampleBitmap2Path.cpp

+/*
+ * Copyright 2011 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 CHAR_BIT 8
+#define SQRT_2 1.41421356237
+
+bool getBit( const char *buffer,

[reed1, 2013/06/13 17:58:41]

any function local to your file... static bool ...

+             const int x ) {

[reed1, 2013/06/13 17:58:41]

for parameters, const on a non-ptr is never meaningful.

+
+    int byte = x / CHAR_BIT;

[reed1, 2013/06/13 17:58:41]

nit: when you know your modulus is a power of two, we often explicitly write &
and >>

e.g.

byte = x >> 8;
bit = x & 7;

Once in a while, the compiler may forget that optimization, and actually
generate a div or mod (ugh)

+    int bit = x % CHAR_BIT;
+
+    return buffer[byte] & (1 << bit);

[reed1, 2013/06/13 17:58:41]

this is not a bool, but an int (which is fine), but you may get a warning as the
compiler turns that into a real 'bool'.

One conversion macro:

bool convertToBool(int predicate) {
    return !!predicate;
or
    return predicate != 0;
}

+}
+
+
+void line2path_pixel( SkPath* path,
+                      const char* line,
+                      const int lineIdx,
+                      const int width ) {
+    for (int i=0; i<width; i++) {
+        // simply makes every ON pixel into a rect path
+        if (getBit(line,i)==1) {                       
+            // add a rect for the pixel
+            SkRect r = { i, lineIdx, i+1, lineIdx+1 };

[reed1, 2013/06/13 17:58:41]

alternate:

SkRect::MakeXYWH(i, lineIdx, 1, 1)

convenience:

path->addRect(SkRect::Make(...), ...);

+            path->addRect(r, SkPath::kCW_Direction);
+        }
+    }
+}
+
+void line2path_pixelCircle( SkPath* path,

[reed1, 2013/06/13 17:58:41]

all these guys can be marked 'static'

+                            const char* line,
+                            const int lineIdx,
+                            const int width ) {
+    for (int i=0; i<width; i++) {

[reed1, 2013/06/13 17:58:41]

very nitty: need more space, and pre-increment

for (int i = 0; i < width; ++i)

+        // simply makes every ON pixel into a circle path
+        if (getBit(line,i)==1) {                       

[reed1, 2013/06/13 17:58:41]

if (getBit(...)) {

+            // add a circle for the pixel
+            path->addCircle( i+.5, lineIdx+.5, SQRT_2 / 2.0 );

[reed1, 2013/06/13 17:58:41]

all 3 params will generate doubles...

use 0.5f if you mean float... or SkFloatToScalar(0.5f)

+        }
+    }
+}
+
+void line2path_span( SkPath* path,
+                     const char* line,
+                     const int lineIdx,
+                     const int width ) {
+    bool state = 0;
+    int start = 1;
+
+    for (int i=0; i<width; i++) {
+        if (i==width-1) { // if the end of a scanline, close open paths
+            if (state==1) {
+                SkRect r = { start, lineIdx,
+                             i+getBit(line,i), lineIdx+1 };
+                path->addRect(r, SkPath::kCW_Direction);
+            } else if (getBit(line,i)==1) {
+                SkRect r = { i, lineIdx,
+                             i+1, lineIdx+1 };
+                path->addRect(r, SkPath::kCW_Direction);
+            }
+            start = 0;
+            state = 0;
+            // if a transition point:
+        }else if (getBit(line,i)!=state) {
+            if (getBit(line,i)==1) { // transition on
+                state = 1; //mark beginning of span
+                start = i;
+            }else { // transition off
+                state = 0;
+                SkRect r = { start, lineIdx,
+                             i, lineIdx+1};
+                path->addRect(r, SkPath::kCW_Direction);
+            }
+        }
+    }
+}
+
+void bitmap2path( SkPath* path,
+                  const char* bitmap,
+                  void (*line2path)( SkPath*,
+                                     const char*,
+                                     const int,
+                                     const int ),
+                  const int h, const int w,
+                  const int stride ) {
+// loop for every line in bitmap
+    for (int i=0; i<h; i++) {
+        line2path(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) {
+        const 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;
+        void (*mode[numModes])( SkPath*, const char*,

[reed1, 2013/06/13 17:58:41]

const void (*....

maybe typdef this guy to a name up above

+                                 const int, const int )
+        = { 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;
+            bitmap2path(&path,bitmap,mode[i],h,w,str);
+
+            //simplify path
+            SkPath simple;
+            Simplify(path, &simple);
+
+            //draw to canvas
+            canvas->save();
+            canvas->scale(10.0, 10.0);

[reed1, 2013/06/13 17:58:41]

more doubles

canvas->scale(10, 10);

+            canvas->translate(10.0*i, 0);
+            canvas->drawPath(simple, paint);
+            canvas->restore();
+        }
+        
+//        this->inval(NULL);
+    }
+
+private:
+    typedef SkView INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static SkView* MyFactory() { return new Bitmap2Path; }
+static SkViewRegister reg(MyFactory);