C 语言中的图像到 ASCII 艺术转换
将位图图像转换为 ASCII 艺术涉及使用等宽字体并保持过程简单。有两种主要方法:
基于像素/区域强度:
此方法将每个像素或像素区域视为单个点。它计算点的平均灰度强度,并将其替换为强度最接近的字符。
字符拟合(混合):
此方法尝试替换区域(字符形状)具有相似强度和形状的字符。它会带来更好的结果,但由于计算而速度较慢。
详细实现:
基于像素/区域强度:
将图像划分为灰度像素或矩形区域(点)。计算每个点的强度。将其替换为强度最接近的字符映射(预先计算的强度)中的字符。
示例字符映射:" .,:;ox%#@&"
强度计算:
<code class="C++">i = p[x+x+x+0]; i += p[x+x+x+1]; i += p[x+x+x+2]; i = (i*l)/768; s += m[l-i];</code>
其中:
字符拟合:
将图像划分为与字符长宽比相同的矩形区域。将字符区域划分为多个区域并计算每个区域的强度。在地图中查找强度和形状最接近的字符。
使用较大字体时,这种方法会带来最佳、视觉上最令人愉悦的结果。
代码示例:
<code class="C++">class intensity { public: char c; // Character int il, ir, iu ,id, ic; // Intensity of part: left,right,up,down,center intensity() { c=0; reset(); } void reset() { il=0; ir=0; iu=0; id=0; ic=0; } void compute(DWORD **p,int xs,int ys,int xx,int yy) // p source image, (xs,ys) area size, (xx,yy) area position { int x0 = xs>>2, y0 = ys>>2; int x1 = xs-x0, y1 = ys-y0; int x, y, i; reset(); for (y=0; y<ys; y++) for (x=0; x<xs; x++) { i = (p[yy+y][xx+x] & 255); if (x<=x0) il+=i; if (x>=x1) ir+=i; if (y<=x0) iu+=i; if (y>=x1) id+=i; if ((x>=x0) && (x<=x1) && (y>=y0) && (y<=y1)) ic+=i; } // Normalize i = xs*ys; il = (il << 8)/i; ir = (ir << 8)/i; iu = (iu << 8)/i; id = (id << 8)/i; ic = (ic << 8)/i; } }; AnsiString bmp2txt_big(Graphics::TBitmap *bmp,TFont *font) // Character sized areas { int i, i0, d, d0; int xs, ys, xf, yf, x, xx, y, yy; DWORD **p = NULL,**q = NULL; // Bitmap direct pixel access Graphics::TBitmap *tmp; // Temporary bitmap for single character AnsiString txt = ""; // Output ASCII art text AnsiString eol = "\r\n"; // End of line sequence intensity map[97]; // Character map intensity gfx; // Input image size xs = bmp->Width; ys = bmp->Height; // Output font size xf = font->Size; if (xf<0) xf =- xf; yf = font->Height; if (yf<0) yf =- yf; for (;;) // Loop to simplify the dynamic allocation error handling { // Allocate and initialise buffers tmp = new Graphics::TBitmap; if (tmp==NULL) break; // Allow 32 bit pixel access as DWORD/int pointer tmp->HandleType = bmDIB; bmp->HandleType = bmDIB; tmp->PixelFormat = pf32bit; bmp->PixelFormat = pf32bit; // Copy target font properties to tmp tmp->Canvas->Font->Assign(font); tmp->SetSize(xf, yf); tmp->Canvas->Font ->Color = clBlack; tmp->Canvas->Pen ->Color = clWhite; tmp->Canvas->Brush->Color = clWhite; xf = tmp->Width; yf = tmp->Height; // Direct pixel access to bitmaps p = new DWORD*[ys]; if (p == NULL) break; for (y=0; y<ys; y++) p[y] = (DWORD*)bmp->ScanLine[y]; q = new DWORD*[yf]; if (q == NULL) break; for (y=0; y<yf; y++) q[y] = (DWORD*)tmp->ScanLine[y]; // Create character map for (x=0, d=32; d<128; d++, x++) { map[x].c = char(DWORD(d)); // Clear tmp tmp->Canvas->FillRect(TRect(0, 0, xf, yf)); // Render tested character to tmp tmp->Canvas->TextOutA(0, 0, map[x].c); // Compute intensity map[x].compute(q, xf, yf, 0, 0); } map[x].c = 0; // Loop through the image by zoomed character size step xf -= xf/3; // Characters are usually overlapping by 1/3 xs -= xs % xf; ys -= ys % yf; for (y=0; y<ys; y+=yf, txt += eol) for (x=0; x<xs; x+=xf) { // Compute intensity gfx.compute(p, xf, yf, x, y); // Find the closest match in map[] i0 = 0; d0 = -1; for (i=0; map[i].c; i++) { d = abs(map[i].il-gfx.il) + abs(map[i].ir-gfx.ir) + abs(map[i].iu-gfx.iu) + abs(map[i].id-gfx.id) + abs(map[i].ic-gfx.ic); if ((d0<0)||(d0>d)) { d0=d; i0=i; } } // Add fitted character to output txt += map[i0].c; } break; } // Free buffers if (tmp) delete tmp; if (p ) delete[] p; return txt; }</code>
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