? ? ? ?在研究非真實感繪制相關算法時，水彩畫算法是第一個開始看的，不過卻拖到最后總結。水彩畫還是挺不好模擬的，里面涉及的算法比較多，本文實現的水彩畫算法主要參考下面兩篇文章，《Interactive watercolor rendering?with temporal coherence and abstraction》 、《Towards Photo Watercolorization?with Artistic Verisimilitude》 ，第一篇文章比較早，第二篇文章比較新，通過這兩篇文章，可以對水彩畫的模擬過程有一個大概了解。不過由于涉及的環節比較多，在實現過程中，有些地方做了簡化，又新增了一些計算環節，總體上得到效果和文章比，并不是嚴格一致，不過本文實現的水彩畫算法運行較慢，還是比較耗時的。 ? ? ? ?水彩畫算法主要涉及的計算環節有：（1）簡化細節；（2）邊緣抖動；（3）邊緣加深；（4）顏料分散；（5）紊流效果；（6）疊加紙張紋理等。上述環節中，簡化細節是非常耗時的，主要是采用了meanshift及各向異性的Kuwahara濾波原因，或許有更好的替代方法，有待優化。本文很多地方使用了噪聲，主要用到了高斯噪聲及柏林噪聲，主要用于模擬邊緣抖動、顏料分散及紊流效果。邊緣抖動有點類似前文水面倒影算法中的置換濾鏡，主要模擬顏料的流動效果。邊緣加深主要模擬顏料停止流動后，在邊緣處的沉淀痕跡。顏料分散及紊流效果，主要是模擬水彩顏料滲透效果。不過本文實現的算法，顏料分散做的不是很滿意，離真實水彩畫那種顏料擴散及滲透效果還有很大差距。 ? ? ? ?下面是部分示例代碼： void* WaterColorThread(void *arg) {WaterColorInfo *watercolor_info = (WaterColorInfo *)arg;BMPINFO *pSrcBitmap = watercolor_info->pSrcBitmap;BMPINFO *pPaperBitmap = watercolor_info->pPaperBitmap;float *noise_perlin = watercolor_info->noise_perlin;float *mean = watercolor_info->mean;float *stdev = watercolor_info->stdev;int color_index = watercolor_info->color_index;int thread_id = watercolor_info->thread_id;int block_count = watercolor_info->block_count;// 數據轉換int width = pSrcBitmap->lWidth;int height= pSrcBitmap->lHeight;int size = width*height;float *rdata = (float *)malloc(size * sizeof(float));float *gdata = (float *)malloc(size * sizeof(float));float *bdata = (float *)malloc(size * sizeof(float));ConvertToFloat(pSrcBitmap, rdata, gdata, bdata);// 簡化細節Abstraction(rdata, gdata, bdata, mean, stdev, width, height, color_index, thread_id);// 邊緣抖動EdgeWobbling(rdata, gdata, bdata, noise_perlin, width, height, block_count);// 邊緣加深EdgeDarkening(rdata, gdata, bdata, 1.5f, width, height);// 顏料分散PigmentDispersion(rdata, gdata, bdata, 0.5f, width, height);// 紊流效果TurbulenceFlow(rdata, gdata, bdata, noise_perlin, 2.0f, width, height);// 紙張紋理PaperTexture(rdata, gdata, bdata, pPaperBitmap, 0.225f, width, height);// 數據轉換ConvertToUchar(rdata, gdata, bdata, pSrcBitmap);// 效果微調ImageAdjust(pSrcBitmap);free(rdata);free(gdata);free(bdata);rdata = NULL;gdata = NULL;bdata = NULL;return NULL; }? ? ? ?邊緣抖動示例代碼： void EdgeWobbling(float *rdata, float *gdata, float *bdata, float *noise_perlin, int width, int height, int block_count) {int size = width*height;float strengthx = width / 3.5f;float strengthy = height*block_count / 3.5f;float strength = MAX(strengthx, strengthy);float *rcopy = (float *)malloc(size * sizeof(float));float *gcopy = (float *)malloc(size * sizeof(float));float *bcopy = (float *)malloc(size * sizeof(float));memcpy(rcopy, rdata, size * sizeof(float));memcpy(gcopy, gdata, size * sizeof(float));memcpy(bcopy, bdata, size * sizeof(float));int index = 0, new_index = 0;int p_offsetx = 0, p_offsety = 0, border_w = width - 1, border_h = height - 1;float *pNoiseData = noise_perlin;for (int i = 0; i < height - 1; i++){for (int j = 0; j < width - 1; j++){index = i*width + j;pNoiseData = noise_perlin + index;float new_posx = CLAMP0255_XY(j + (*(pNoiseData + 1) - *pNoiseData) * strength, border_w);float new_posy = CLAMP0255_XY(i + (*(pNoiseData + width) - *pNoiseData) * strength, border_h);int n_posx = (int)new_posx;int n_posy = (int)new_posy;float dx = new_posx - n_posx;float dy = new_posy - n_posy;p_offsetx = (n_posx != border_w);p_offsety = (n_posy != border_h);float r0 = 0.0f, g0 = 0.0f, b0 = 0.0f, r1 = 0.0f, g1 = 0.0f, b1 = 0.0f;new_index = n_posy*width + n_posx;r0 = *(rcopy + new_index);g0 = *(gcopy + new_index);b0 = *(bcopy + new_index);r1 = *(rcopy + new_index + p_offsetx);g1 = *(gcopy + new_index + p_offsetx);b1 = *(bcopy + new_index + p_offsetx);float r2 = 0.0f, g2 = 0.0f, b2 = 0.0f, r3 = 0.0f, g3 = 0.0f, b3 = 0.0f;new_index = (n_posy + p_offsety)*width + n_posx;r2 = *(rcopy + new_index);g2 = *(gcopy + new_index);b2 = *(bcopy + new_index);r3 = *(rcopy + new_index + p_offsetx);g3 = *(gcopy + new_index + p_offsetx);b3 = *(bcopy + new_index + p_offsetx);float r_val = 0.0f, g_val = 0.0f, b_val = 0.0f, fx1 = 0.0f, fx2 = 0.0f;fx1 = r0 + (r1 - r0) * dx;fx2 = r2 + (r3 - r2) * dx;r_val = fx1 + (fx2 - fx1) * dy;fx1 = g0 + (g1 - g0) * dx;fx2 = g2 + (g3 - g2) * dx;g_val = fx1 + (fx2 - fx1) * dy;fx1 = b0 + (b1 - b0) * dx;fx2 = b2 + (b3 - b2) * dx;b_val = fx1 + (fx2 - fx1) * dy;*(rdata + index) = *(rcopy + index)*0.4f + r_val*0.6f;*(gdata + index) = *(gcopy + index)*0.4f + g_val*0.6f;*(bdata + index) = *(bcopy + index)*0.4f + b_val*0.6f;}}free(rcopy);rcopy = NULL;free(gcopy);gcopy = NULL;free(bcopy);bcopy = NULL; }? ? ? ?邊緣加深示例代碼： void EdgeDarkening(float *rdata, float *gdata, float *bdata, float strength, int width, int height) {int step = width;int size = width*height;float *rcopy = (float *)malloc(size * sizeof(float));float *gcopy = (float *)malloc(size * sizeof(float));float *bcopy = (float *)malloc(size * sizeof(float));memcpy(rcopy, rdata, size * sizeof(float));memcpy(gcopy, gdata, size * sizeof(float));memcpy(bcopy, bdata, size * sizeof(float));int index = 0;float *pSrcRData = NULL, *pSrcGData = NULL, *pSrcBData = NULL;float *pNewRData = NULL, *pNewGData = NULL, *pNewBData = NULL;float *pLeftData = NULL, *pRightData = NULL, *pUpData = NULL, *pDownData = NULL;for (int i = 1; i < height - 1; i++){for (int j = 1; j < width - 1; j++){index = i*width + j;// redpNewRData = rcopy + index;pLeftData = pNewRData - 1;pRightData = pNewRData + 1;pUpData = pNewRData - step;pDownData = pNewRData + step;float gradient_r = fabs(*pRightData - *pLeftData) + fabs(*pDownData - *pUpData);// greenpNewGData = gcopy + index;pLeftData = pNewGData - 1;pRightData = pNewGData + 1;pUpData = pNewGData - step;pDownData = pNewGData + step;float gradient_g = fabs(*pRightData - *pLeftData) + fabs(*pDownData - *pUpData);// bluepNewBData = bcopy + index;pLeftData = pNewBData - 1;pRightData = pNewBData + 1;pUpData = pNewBData - step;pDownData = pNewBData + step;float gradient_b = fabs(*pRightData - *pLeftData) + fabs(*pDownData - *pUpData);// resultfloat gradient = (gradient_r + gradient_g + gradient_b)/* / 1.0f*/;pSrcRData = rdata + index;pSrcGData = gdata + index;pSrcBData = bdata + index;*pSrcRData = (float)CLAMP0255_XY(BousseauColorModel(*pSrcRData, gradient, strength), 1.0f);*pSrcGData = (float)CLAMP0255_XY(BousseauColorModel(*pSrcGData, gradient, strength), 1.0f);*pSrcBData = (float)CLAMP0255_XY(BousseauColorModel(*pSrcBData, gradient, strength), 1.0f);}}free(rcopy);rcopy = NULL;free(gcopy);gcopy = NULL;free(bcopy);bcopy = NULL; }? ? ? ?顏料分散示例代碼： void PigmentDispersion(float *rdata, float *gdata, float *bdata, float strength, int width, int height) {int size = width*height;float *noise_gaussian = (float *)malloc(size * sizeof(float));GaussianNoise(noise_gaussian, width, height);float *pSrcRData = rdata, *pSrcGData = gdata, *pSrcBData = bdata;for (int i = 0; i < size; i++, pSrcRData++, pSrcGData++, pSrcBData++){*pSrcRData = (float)CLAMP0255_XY(BousseauColorModel(*pSrcRData, noise_gaussian[i], strength), 1.0f);*pSrcGData = (float)CLAMP0255_XY(BousseauColorModel(*pSrcGData, noise_gaussian[i], strength), 1.0f);*pSrcBData = (float)CLAMP0255_XY(BousseauColorModel(*pSrcBData, noise_gaussian[i], strength), 1.0f);}free(noise_gaussian);noise_gaussian = NULL; }? ? ? ?如果顏料分散模擬的好，感覺還是有水彩畫那么點意思的，不過現在也懶得優化了，下面是一些效果圖：
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? ? ? ?也歡迎下載示例demo：http://download.csdn.net/detail/u013085897/9747177

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