How do you convert a bitmap image to ASCII art in C ?

Image to ASCII art conversion in C

Converting a bitmap image to ASCII art involves using mono-spaced fonts and keeping the process simple. There are two main approaches:

Pixel/area intensity based:

This approach treats each pixel or area of pixels as a single dot. It computes the average gray scale intensity of the dot and replaces it with a character of closest intensity.

Character fitting (hybrid):

This approach tries to replace areas (character shaped) with characters of similar intensity and shape. It leads to better results but is slower due to computations.

Detailed Implementation:

Pixel/area intensity based:

Divide the image into gray-scale pixels or rectangular areas (dots). Compute the intensity of each dot. Replace it with a character from a character map (precomputed intensities) with the closest intensity.

A sample character map: " .,:;ox%#@&"

Intensity computation:

<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>

where:

• i is the summation of pixel intensities
• l is the length of the character map
• m is the character map
• s is the output string

Character fitting:

Divide the image into rectangular areas with the same aspect ratio as the characters. Divide the character area into zones and compute the intensity of each zone. Find the character in the map with the closest intensity and shape fit.

This approach leads to best, most visually pleasing results when using larger fonts.

Code Example:

<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 i="(p[yy+y][xx+x]" if il>=x1) ir+=i;
                if (y=x1) id+=i;

                if ((x>=x0) && (x=y0) && (yWidth;
    ys = bmp->Height;

    // Output font size
    xf = font->Size;   if (xfHeight; if (yfHandleType = 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>ScanLine[y];

        q  = new DWORD*[yf];
        if (q  == NULL) break;
        for (y=0; y<yf y q>ScanLine[y];

        // Create character map
        for (x=0, d=32; dCanvas->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 txt eol for x compute intensity gfx.compute xf yf find the closest match in map i0="0;" d0="-1;" i d="abs(map[i].il-gfx.il)" abs if>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;
}</ys></yf></ys></ys></code>

The above is the detailed content of How do you convert a bitmap image to ASCII art in C ?. For more information, please follow other related articles on the PHP Chinese website!