bilinearExpandPowerOf2()

void fl::bilinearExpandPowerOf2	(	const CRGB *	input,
		CRGB *	output,
		uint8_t	inputWidth,
		uint8_t	inputHeight,
		fl::XYMap	xyMap )

Performs bilinear interpolation for upscaling an image.

Parameters

output	The output grid to write into the interpolated values.
input	The input grid to read from.
inputWidth	The width of the input grid.
inputHeight	The height of the input grid.
xyMap	The XYMap to use to determine where to write the pixel. If the pixel is mapped outside of the range then it is clipped.

Definition at line 86 of file bilinear_expansion.cpp.

                                                                                                                   {
    uint8_t width = xyMap.getWidth();
    uint8_t height = xyMap.getHeight();
    if (width != xyMap.getWidth() || height != xyMap.getHeight()) {
        // xyMap has width and height that do not fit in an uint16_t.
        return;
    }
    uint16_t n = xyMap.getTotal();
 
    for (uint8_t y = 0; y < height; y++) {
        for (uint8_t x = 0; x < width; x++) {
            // Use 8-bit fixed-point arithmetic with 8 fractional bits
            // (scale factor of 256)
            uint16_t fx = ((uint16_t)x * (inputWidth - 1) * 256) / (width - 1);
            uint16_t fy =
                ((uint16_t)y * (inputHeight - 1) * 256) / (height - 1);
 
            uint8_t ix = fx >> 8; // Integer part
            uint8_t iy = fy >> 8;
            uint8_t dx = fx & 0xFF; // Fractional part
            uint8_t dy = fy & 0xFF;
 
            uint8_t ix1 = (ix + 1 < inputWidth) ? ix + 1 : ix;
            uint8_t iy1 = (iy + 1 < inputHeight) ? iy + 1 : iy;
 
            uint16_t i00 = iy * inputWidth + ix;
            uint16_t i10 = iy * inputWidth + ix1;
            uint16_t i01 = iy1 * inputWidth + ix;
            uint16_t i11 = iy1 * inputWidth + ix1;
 
            CRGB c00 = input[i00];
            CRGB c10 = input[i10];
            CRGB c01 = input[i01];
            CRGB c11 = input[i11];
 
            CRGB result;
            result.r = bilinearInterpolatePowerOf2(c00.r, c10.r, c01.r, c11.r, dx, dy);
            result.g = bilinearInterpolatePowerOf2(c00.g, c10.g, c01.g, c11.g, dx, dy);
            result.b = bilinearInterpolatePowerOf2(c00.b, c10.b, c01.b, c11.b, dx, dy);
 
            uint16_t idx = xyMap.mapToIndex(x, y);
            if (idx < n) {
                output[idx] = result;
            }
        }
    }
}

References bilinearInterpolatePowerOf2(), x, xyMap, and y.

Referenced by bilinearExpand(), and fl::ScaleUp::expand().

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