first cut at rubber-sheet warping

git-svn-id: http://skia.googlecode.com/svn/trunk@401 2bbb7eff-a529-9590-31e7-b0007b416f81

samplecode/SampleWarp.cpp

@@ -0,0 +1,211 @@
+#include "SampleCode.h"
+#include "SkView.h"
+#include "SkCanvas.h"
+#include "SkGradientShader.h"
+#include "SkPath.h"
+#include "SkRegion.h"
+#include "SkShader.h"
+#include "SkUtils.h"
+#include "SkImageDecoder.h"
+
+class Mesh {
+public:
+    Mesh();
+    ~Mesh();
+
+    Mesh& operator=(const Mesh& src);
+
+    void init(const SkRect& bounds, int rows, int cols,
+              const SkRect& texture);
+
+    int rows() const { return fRows; }
+    int cols() const { return fCols; }
+    SkPoint& pt(int row, int col) {
+        return fPts[row * (fRows + 1) + col];
+    }
+
+    void draw(SkCanvas*, const SkPaint&);
+    void drawWireframe(SkCanvas* canvas, const SkPaint& paint);
+
+private:
+    int         fRows, fCols;
+    SkPoint*    fPts;
+    SkPoint*    fTex;   // just points into fPts, not separately allocated
+    int         fCount;
+    uint16_t*   fIndices;
+    int         fIndexCount;
+};
+
+Mesh::Mesh() : fPts(NULL), fCount(0), fIndices(NULL), fIndexCount(0) {}
+
+Mesh::~Mesh() {
+    delete[] fPts;
+    delete[] fIndices;
+}
+
+Mesh& Mesh::operator=(const Mesh& src) {
+    delete[] fPts;
+    delete[] fIndices;
+
+    fRows = src.fRows;
+    fCols = src.fCols;
+
+    fCount = src.fCount;
+    fPts = new SkPoint[fCount * 2];
+    fTex = fPts + fCount;
+    memcpy(fPts, src.fPts, fCount * 2 * sizeof(SkPoint));
+    
+    delete[] fIndices;
+    fIndexCount = src.fIndexCount;
+    fIndices = new uint16_t[fIndexCount];
+    memcpy(fIndices, src.fIndices, fIndexCount * sizeof(uint16_t));
+
+    return *this;
+}
+
+void Mesh::init(const SkRect& bounds, int rows, int cols,
+                const SkRect& texture) {
+    SkASSERT(rows > 0 && cols > 0);
+
+    fRows = rows;
+    fCols = cols;
+
+    delete[] fPts;
+    fCount = (rows + 1) * (cols + 1);
+    fPts = new SkPoint[fCount * 2];
+    fTex = fPts + fCount;
+
+    delete[] fIndices;
+    fIndexCount = rows * cols * 6;
+    fIndices = new uint16_t[fIndexCount];
+    
+    SkPoint* pts = fPts;
+    const SkScalar dx = bounds.width() / rows;
+    const SkScalar dy = bounds.height() / cols;
+    SkPoint* tex = fTex;
+    const SkScalar dtx = texture.width() / rows;
+    const SkScalar dty = texture.height() / cols;
+    uint16_t* idx = fIndices;
+    int index = 0;
+    for (int y = 0; y <= cols; y++) {
+        for (int x = 0; x <= rows; x++) {
+            pts->set(bounds.fLeft + x*dx, bounds.fTop + y*dy);
+            pts += 1;
+            tex->set(texture.fLeft + x*dtx, texture.fTop + y*dty);
+            tex += 1;
+            
+            if (y < cols && x < rows) {
+                *idx++ = index;
+                *idx++ = index + rows + 1;
+                *idx++ = index + 1;
+
+                *idx++ = index + 1;
+                *idx++ = index + rows + 1;
+                *idx++ = index + rows + 2;
+                
+                index += 1;
+            }
+        }
+        index += 1;
+    }
+}
+
+void Mesh::draw(SkCanvas* canvas, const SkPaint& paint) {
+    canvas->drawVertices(SkCanvas::kTriangles_VertexMode, fCount,
+                         fPts, fTex, NULL, NULL, fIndices, fIndexCount,
+                         paint);
+}
+
+void Mesh::drawWireframe(SkCanvas* canvas, const SkPaint& paint) {
+    canvas->drawVertices(SkCanvas::kTriangles_VertexMode, fCount,
+                         fPts, NULL, NULL, NULL, fIndices, fIndexCount,
+                         paint);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+class WarpView : public SkView {
+    Mesh        fMesh, fOrig;
+    SkBitmap    fBitmap;
+public:
+	WarpView() {
+        SkBitmap bm;
+        SkImageDecoder::DecodeFile("/skimages/nytimes.png", &bm);
+        SkIRect subset = { 0, 0, 420, 420 };
+        bm.extractSubset(&fBitmap, subset);
+        
+        SkRect bounds, texture;
+        texture.set(0, 0, SkIntToScalar(fBitmap.width()),
+                    SkIntToScalar(fBitmap.height()));
+        bounds = texture;
+        
+//        fMesh.init(bounds, fBitmap.width() / 40, fBitmap.height() / 40, texture);
+        fMesh.init(bounds, 10, 10, texture);
+        fOrig = fMesh;
+    }
+
+protected:
+    // overrides from SkEventSink
+    virtual bool onQuery(SkEvent* evt) {
+        if (SampleCode::TitleQ(*evt)) {
+            SampleCode::TitleR(evt, "Warp");
+            return true;
+        }
+        return this->INHERITED::onQuery(evt);
+    }
+    
+    void warp(const SkPoint& p0, const SkPoint& p1) {
+        int rows = fMesh.rows();
+        int cols = fMesh.cols();
+        
+        const SkVector delta = p1 - p0;
+        for (int y = 1; y < cols; y++) {
+            for (int x = 1; x < rows; x++) {
+                const SkPoint& orig = fOrig.pt(x, y);
+                SkScalar dist = SkPoint::Distance(p0, orig);
+                dist += SkIntToScalar(1);
+          //      dist = SkScalarSqrt(dist);
+                SkScalar dx = SkScalarDiv(delta.fX, dist);
+                SkScalar dy = SkScalarDiv(delta.fY, dist);
+                fMesh.pt(x, y).set(orig.fX + dx, orig.fY + dy);
+//                SkDebugf("[%g %g] -> [%d %d %g] <%g %g>\n", delta.fX, delta.fY, x, y, dist, dx, dy);
+            }
+        }
+    }
+    
+    virtual void onDraw(SkCanvas* canvas) {
+        canvas->drawColor(SK_ColorGRAY);
+        
+        SkPaint paint;
+        paint.setFilterBitmap(true);
+        paint.setShader(SkShader::CreateBitmapShader(fBitmap,
+                                                     SkShader::kClamp_TileMode,
+                                                     SkShader::kClamp_TileMode))->unref();
+        fMesh.draw(canvas, paint);
+        
+        paint.setShader(NULL);
+        paint.setColor(SK_ColorRED);
+        fMesh.draw(canvas, paint);
+    }
+    
+    virtual SkView::Click* onFindClickHandler(SkScalar x, SkScalar y) {
+        return new Click(this);
+    }
+    
+    virtual bool onClick(Click* click) {
+        this->warp(click->fOrig, click->fCurr);
+        this->inval(NULL);
+        return true;
+    }
+    
+private:
+    SkIRect    fBase, fRect;
+    
+    typedef SkView INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static SkView* MyFactory() { return new WarpView; }
+static SkViewRegister reg(MyFactory);
+