■ Bitmap 클래스에서 그라디언트 기반 가장자리 탐지 필터(Gradient Based Edge Detection Filter)를 사용하는 방법을 보여준다.
▶ 예제 코드 (C#)
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using System; using System.Drawing; using System.Drawing.Imaging; using System.Runtime.InteropServices; #region 그라디언트 기반 가장자리 탐지 필터 적용하기 - ApplyGradientBasedEdgeDetectionFilter(sourceBitmap, edgeColor, threshold) /// <summary> /// 그라디언트 기반 가장자리 탐지 필터 적용하기 /// </summary> /// <param name="sourceBitmap">소스 비트맵</param> /// <param name="edgeColor">가장자리 색상</param> /// <param name="threshold">임계치</param> /// <returns>비트맵</returns> public Bitmap ApplyGradientBasedEdgeDetectionFilter(Bitmap sourceBitmap, Color edgeColor, byte threshold = 0) { BitmapData sourceBitmapData = sourceBitmap.LockBits ( new Rectangle (0, 0, sourceBitmap.Width, sourceBitmap.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb ); byte[] sourceByteArray = new byte[sourceBitmapData.Stride * sourceBitmapData.Height]; byte[] targetByteArray = new byte[sourceBitmapData.Stride * sourceBitmapData.Height]; Marshal.Copy(sourceBitmapData.Scan0, sourceByteArray, 0, sourceByteArray.Length); Marshal.Copy(sourceBitmapData.Scan0, targetByteArray, 0, targetByteArray.Length); sourceBitmap.UnlockBits(sourceBitmapData); int sourceOffset = 0; int gradientValue = 0; bool exceedThreshold = false; for(int offsetY = 1; offsetY < sourceBitmap.Height - 1; offsetY++) { for(int offsetX = 1; offsetX < sourceBitmap.Width - 1; offsetX++) { sourceOffset = offsetY * sourceBitmapData.Stride + offsetX * 4; gradientValue = 0; exceedThreshold = true; CheckThreshold ( sourceByteArray, sourceOffset - 4, sourceOffset + 4, ref gradientValue, threshold, 2 ); exceedThreshold = CheckThreshold ( sourceByteArray, sourceOffset - sourceBitmapData.Stride, sourceOffset + sourceBitmapData.Stride, ref gradientValue, threshold, 2 ); if(exceedThreshold == false) { gradientValue = 0; exceedThreshold = CheckThreshold ( sourceByteArray, sourceOffset - 4, sourceOffset + 4, ref gradientValue, threshold ); if(exceedThreshold == false) { gradientValue = 0; exceedThreshold = CheckThreshold ( sourceByteArray, sourceOffset - sourceBitmapData.Stride, sourceOffset + sourceBitmapData.Stride, ref gradientValue, threshold ); if(exceedThreshold == false) { gradientValue = 0; CheckThreshold ( sourceByteArray, sourceOffset - 4 - sourceBitmapData.Stride, sourceOffset + 4 + sourceBitmapData.Stride, ref gradientValue, threshold, 2 ); exceedThreshold = CheckThreshold ( sourceByteArray, sourceOffset - sourceBitmapData.Stride + 4, sourceOffset - 4 + sourceBitmapData.Stride, ref gradientValue, threshold, 2 ); if(exceedThreshold == false) { gradientValue = 0; exceedThreshold = CheckThreshold ( sourceByteArray, sourceOffset - 4 - sourceBitmapData.Stride, sourceOffset + 4 + sourceBitmapData.Stride, ref gradientValue, threshold ); if(exceedThreshold == false) { gradientValue = 0; exceedThreshold = CheckThreshold ( sourceByteArray, sourceOffset - sourceBitmapData.Stride + 4, sourceOffset + sourceBitmapData.Stride - 4, ref gradientValue, threshold ); } } } } } if(exceedThreshold == true) { targetByteArray[sourceOffset ] = edgeColor.B; targetByteArray[sourceOffset + 1] = edgeColor.G; targetByteArray[sourceOffset + 2] = edgeColor.R; } targetByteArray[sourceOffset + 3] = 255; } } Bitmap targetBitmap = new Bitmap(sourceBitmap.Width, sourceBitmap.Height); BitmapData targetBitmapData = targetBitmap.LockBits ( new Rectangle(0, 0, targetBitmap.Width, targetBitmap.Height), ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb ); Marshal.Copy(targetByteArray, 0, targetBitmapData.Scan0, targetByteArray.Length); targetBitmap.UnlockBits(targetBitmapData); return targetBitmap; } #endregion #region 임계치 체크하기 - CheckThreshold(sourceByteArray, offset1, offset2, gradientValue, threshold, divideBy) /// <summary> /// 임계치 체크하기 /// </summary> /// <param name="sourceByteArray">소스 바이트 배열</param> /// <param name="offset1">오프셋 1</param> /// <param name="offset2">오프셋 2</param> /// <param name="gradientValue">그라디언트 값</param> /// <param name="threshold">임계치</param> /// <param name="divideBy">젯수</param> /// <returns>임계치 체크 결과</returns> private bool CheckThreshold ( byte[] sourceByteArray, int offset1, int offset2, ref int gradientValue, byte threshold, int divideBy = 1 ) { gradientValue += Math.Abs(sourceByteArray[offset1 ] - sourceByteArray[offset2 ]) / divideBy; gradientValue += Math.Abs(sourceByteArray[offset1 + 1] - sourceByteArray[offset2 + 1]) / divideBy; gradientValue += Math.Abs(sourceByteArray[offset1 + 2] - sourceByteArray[offset2 + 2]) / divideBy; return (gradientValue >= threshold); } #endregion |