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[rtextures] fix bad behaviour of GenImageGradientLinear with certain angle values. #4462

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Nov 4, 2024
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[rtextures] fix bad behaviour of GenImageGradientLinear with certain angle values. #4462

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17 changes: 14 additions & 3 deletions src/rtextures.c
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Original file line number Diff line number Diff line change
Expand Up @@ -827,16 +827,27 @@ Image GenImageGradientLinear(int width, int height, int direction, Color start,
float cosDir = cosf(radianDirection);
float sinDir = sinf(radianDirection);

// Calculate how far the top-left pixel is along the gradient direction from the center of said gradient
float startingPos = 0.5 - (cosDir*width/2) - (sinDir*height/2);
// With directions that lie in the first or third quadrant (i.e. from top-left to
// bottom-right or vice-versa), pixel (0, 0) is the farthest point on the gradient
// (i.e. the pixel which should become one of the gradient's ends color); while for
// directions that lie in the second or fourth quadrant, that point is pixel (width, 0).
float maxPosValue =
((signbit(sinDir) != 0) == (signbit(cosDir) != 0))
? fabs(startingPos)
: fabs(startingPos+width*cosDir);
for (int i = 0; i < width; i++)
{
for (int j = 0; j < height; j++)
{
// Calculate the relative position of the pixel along the gradient direction
float pos = (i*cosDir + j*sinDir)/(width*cosDir + height*sinDir);
float pos = (startingPos + (i*cosDir + j*sinDir)) / maxPosValue;

float factor = pos;
factor = (factor > 1.0f)? 1.0f : factor; // Clamp to [0,1]
factor = (factor < 0.0f)? 0.0f : factor; // Clamp to [0,1]
factor = (factor > 1.0f)? 1.0f : factor; // Clamp to [-1,1]
factor = (factor < -1.0f)? -1.0f : factor; // Clamp to [-1,1]
factor = factor / 2 + 0.5f;

// Generate the color for this pixel
pixels[j*width + i].r = (int)((float)end.r*factor + (float)start.r*(1.0f - factor));
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