Libharu pdf创建：如何知道打印文本的大小

Question

我目前正在使用libharu 库以便在 C++ 程序中呈现一些 pdf。

我不知道是否有可能知道使用特定字体绘制特定文本所需的大小。

HPDF_Page_TextRect 绘图方法将返回 HPDF_PAGE_INSUFFICIENT_SPACE 消息，如果文本不能适合提供的矩形，但我想知道是否有一种方法来计算文本的最小大小适合特定字体。

提前谢谢。

Answer 1

我找到了一种解决方法，即在页面外绘制文本，同时缩小矩形宽度，直到绘制失败。它一点也不精巧，但它确实有效。

HPDF_STATUS drawString_2(HPDF_Page pdfPage, CString texte, COLORREF textColor, HPDF_Font font, HPDF_REAL fontSize, HPDF_REAL left, HPDF_REAL right, HPDF_REAL top, 
                         HPDF_REAL bottom, HPDF_TextAlignment alignment, HPDF_REAL textRise = 0, HPDF_TextRenderingMode renderingMode = HPDF_FILL);


HPDF_REAL calculateMaxWidthForTextInRect2(HPDF_Page pdfPage, CString texte, HPDF_REAL left, HPDF_REAL right, HPDF_REAL top, HPDF_REAL bottom, HPDF_Font font, HPDF_REAL fontSize);


HPDF_STATUS drawString_2(HPDF_Page pdfPage, CString texte, COLORREF textColor, HPDF_Font font, HPDF_REAL fontSize, HPDF_REAL left, HPDF_REAL right, HPDF_REAL top, 
                         HPDF_REAL bottom, HPDF_TextAlignment alignment, HPDF_REAL textRise, HPDF_TextRenderingMode renderingMode)
{
#ifdef DEBUG
        assert(font != NULL);
#else
        if (font == NULL)
            return 1;
#endif
    HPDF_Page_SetFontAndSize(pdfPage, font, fontSize);
    HPDF_Page_SetTextRise(pdfPage, textRise);
    HPDF_Page_SetTextRenderingMode(pdfPage, renderingMode);
    HPDF_Page_SetRGBFill(pdfPage, GetRValue(textColor) / 255.f, GetGValue(textColor) / 255.f, GetBValue(textColor) / 255.f);
    HPDF_Page_BeginText(pdfPage);
    HPDF_STATUS returnValue = HPDF_Page_TextRect(pdfPage, left, top, right, bottom, (LPCSTR)texte, alignment, NULL);
    HPDF_Page_EndText(pdfPage);

    return returnValue;
}

HPDF_REAL calculateMaxWidthForTextInRect2(HPDF_Page pdfPage, CString texte, HPDF_REAL left, HPDF_REAL right, HPDF_REAL top, HPDF_REAL bottom, HPDF_Font font, HPDF_REAL fontSize)
{
    // Let's draw outside the page size, so the text, even invisible, will not be selectionnable and copyable
    HPDF_REAL leftTmp           = -(right - left);
    HPDF_REAL rightTmp          = 0;
    HPDF_REAL topTmp            = -(bottom - top);
    HPDF_REAL bottomTmp         = 0;

    HPDF_Page_SetTextRenderingMode(pdfPage, HPDF_INVISIBLE);

    // Let's reduce horizontally the rect until the drawing fails
    while (drawString_2(pdfPage, texte, RGB(0, 0, 0), font, fontSize, leftTmp, rightTmp, topTmp, bottomTmp, HPDF_TALIGN_CENTER, 0, HPDF_INVISIBLE) == HPDF_OK)
    {
        leftTmp ++;
        rightTmp --;
    }   

    // If no drawing has be performed, the text cannot be rendered in the provided rect
    if (rightTmp == 0)
        return -1;

    // Let's decrement the shifting in order to get the latest correct value
    leftTmp --;
    rightTmp ++;

    return (rightTmp - leftTmp);
}

Answer 2

另一种方法是使用HPDF_Page_TextWidth函数获取当前字体大小、字符间距和字间距的文本宽度：

HPDF_STATUS FitText( 
                    HPDF_Page pdfPage, 
                    HPDF_Font pdfFont, 
                    HPDF_REAL pdfFontSize, 
                    HPDF_REAL rectProvidedLeft, 
                    HPDF_REAL rectProvidedRight, 
                    HPDF_REAL rectProvidedTop, 
                    char *pText )
{
    if ( pdfPage <= 0 || pdfFont <= 0 || pdfFontSize <= 0 )
        return HPDF_INVALID_PARAMETER;

    HPDF_Page_SetFontAndSize ( pdfPage, pdfFont, pdfFontSize );
    HPDF_REAL dTextExtent = HPDF_Page_TextWidth ( pdfPage, pText );

    // reduce font size until text fit in provided rectangle
    HPDF_REAL nReducedFontSize = pdfFontSize;
    while ( dTextExtent > (rectProvidedRight-rectProvidedLeft) && nReducedFontSize >= 0 )
    {
        HPDF_Page_SetFontAndSize ( pdfPage, pdfFont, --nReducedFontSize );
        dTextExtent         = HPDF_Page_TextWidth ( pdfPage, pText );
    }
    if ( nReducedFontSize == 0 )
        return HPDF_STRING_OUT_OF_RANGE;

    HPDF_Page_BeginText     ( pdfPage );
    HPDF_Page_MoveTextPos   ( pdfPage, rectProvidedLeft, rectProvidedTop );
    HPDF_STATUS pdfStatus   = HPDF_Page_ShowText    ( pdfPage, pText );
    HPDF_Page_EndText       ( pdfPage );

    return pdfStatus;
}