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svg_loader: define the scaling factors for units changing

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The values in absolute units are calculated based on the pixel unit.
Till now the default value of 90dpi was used. Since CSS3 (now CSS4 is
the most recent) 1 inch equals to 96 pixels. The necessary constants
are introduces in this commit.
This commit is contained in:
Mira Grudzinska 2021-10-10 23:41:52 +02:00 • committed by Mira Grudzinska
parent 3c7d037841
commit 7176a5ddd4
1 changed files with 21 additions and 15 deletions
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36
src/loaders/svg/tvgSvgLoader.cpp
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@ -64,6 +64,17 @@
/* Internal Class Implementation */
/************************************************************************/
/*
* According to: https://www.w3.org/TR/SVG2/coords.html#Units
* and: https://www.w3.org/TR/css-values-4/#absolute-lengths
*/
#define PX_PER_IN 96 //1 in = 96 px
#define PX_PER_PC 16 //1 pc = 1/6 in -> PX_PER_IN/6
#define PX_PER_PT 1.333333f //1 pt = 1/72 in -> PX_PER_IN/72
#define PX_PER_MM 3.779528f //1 in = 25.4 mm -> PX_PER_IN/25.4
#define PX_PER_CM 37.79528f //1 in = 2.54 cm -> PX_PER_IN/2.54
typedef SvgNode* (*FactoryMethod)(SvgLoaderData* loader, SvgNode* parent, const char* buf, unsigned bufLength);
typedef SvgStyleGradient* (*GradientFactoryMethod)(SvgLoaderData* loader, const char* buf, unsigned bufLength);
@ -107,20 +118,16 @@ static bool _parseNumber(const char** content, float* number)
/**
* According to https://www.w3.org/TR/SVG/coords.html#Units
*
* TODO
* Since this documentation is not obvious, more clean recalculation with dpi
* is required, but for now default w3 constants would be used
*/
static float _toFloat(const SvgParser* svgParse, const char* str, SvgParserLengthType type)
{
float parsedValue = svgUtilStrtof(str, nullptr);
if (strstr(str, "cm")) parsedValue = parsedValue * 35.43307;
else if (strstr(str, "mm")) parsedValue = parsedValue * 3.543307;
else if (strstr(str, "pt")) parsedValue = parsedValue * 1.25;
else if (strstr(str, "pc")) parsedValue = parsedValue * 15;
else if (strstr(str, "in")) parsedValue = parsedValue * 90;
if (strstr(str, "cm")) parsedValue *= PX_PER_CM;
else if (strstr(str, "mm")) parsedValue *= PX_PER_MM;
else if (strstr(str, "pt")) parsedValue *= PX_PER_PT;
else if (strstr(str, "pc")) parsedValue *= PX_PER_PC;
else if (strstr(str, "in")) parsedValue *= PX_PER_IN;
else if (strstr(str, "%")) {
if (type == SvgParserLengthType::Vertical) parsedValue = (parsedValue / 100.0) * svgParse->global.h;
else if (type == SvgParserLengthType::Horizontal) parsedValue = (parsedValue / 100.0) * svgParse->global.w;
@ -132,7 +139,6 @@ static float _toFloat(const SvgParser* svgParse, const char* str, SvgParserLengt
parsedValue = (parsedValue / 100.0) * max;
}
}
//TODO: Implement 'em', 'ex' attributes
return parsedValue;
@ -150,11 +156,11 @@ static float _gradientToFloat(const SvgParser* svgParse, const char* str, bool&
parsedValue = parsedValue / 100.0;
isPercentage = true;
}
else if (strstr(str, "cm")) parsedValue = parsedValue * 35.43307;
else if (strstr(str, "mm")) parsedValue = parsedValue * 3.543307;
else if (strstr(str, "pt")) parsedValue = parsedValue * 1.25;
else if (strstr(str, "pc")) parsedValue = parsedValue * 15;
else if (strstr(str, "in")) parsedValue = parsedValue * 90;
else if (strstr(str, "cm")) parsedValue *= PX_PER_CM;
else if (strstr(str, "mm")) parsedValue *= PX_PER_MM;
else if (strstr(str, "pt")) parsedValue *= PX_PER_PT;
else if (strstr(str, "pc")) parsedValue *= PX_PER_PC;
else if (strstr(str, "in")) parsedValue *= PX_PER_IN;
//TODO: Implement 'em', 'ex' attributes
return parsedValue;