Yang Junyao 201090191
Diff: N5110.cpp
- Revision:
- 43:c2598020fcac
- Parent:
- 42:596c207519de
- Child:
- 44:57f9d32fb521
--- a/N5110.cpp Tue Mar 21 10:43:19 2017 +0000 +++ b/N5110.cpp Tue Mar 21 11:46:14 2017 +0000 @@ -370,12 +370,13 @@ unsigned int const y1, unsigned int const type) { - int y_range = y1-y0; // calc range of y and x - int x_range = x1-x0; - int start,stop,step; + // Note that the ranges can be negative so we have to turn the input values + // into signed integers first + int const y_range = static_cast<int>(y1) - static_cast<int>(y0); + int const x_range = static_cast<int>(x1) - static_cast<int>(x0); // if dotted line, set step to 2, else step is 1 - step = (type==2) ? 2:1; + unsigned int const step = (type==2) ? 2:1; // make sure we loop over the largest range to get the most pixels on the display // for instance, if drawing a vertical line (x_range = 0), we need to loop down the y pixels @@ -383,13 +384,14 @@ if ( abs(x_range) > abs(y_range) ) { // ensure we loop from smallest to largest or else for-loop won't run as expected - start = x1>x0 ? x0:x1; - stop = x1>x0 ? x1:x0; + unsigned int const start = x_range > 0 ? x0:x1; + unsigned int const stop = x_range > 0 ? x1:x0; // loop between x pixels - for (int x = start; x<= stop ; x+=step) { + for (unsigned int x = start; x<= stop ; x+=step) { // do linear interpolation - int y = y0 + (y1-y0)*(x-x0)/(x1-x0); + int const dx = static_cast<int>(x)-static_cast<int>(x0); + unsigned int const y = y0 + y_range * dx / x_range; // If the line type is '0', this will clear the pixel // If it is '1' or '2', the pixel will be set @@ -398,12 +400,13 @@ } else { // ensure we loop from smallest to largest or else for-loop won't run as expected - start = y1>y0 ? y0:y1; - stop = y1>y0 ? y1:y0; + unsigned int const start = y_range > 0 ? y0:y1; + unsigned int const stop = y_range > 0 ? y1:y0; - for (int y = start; y<= stop ; y+=step) { + for (unsigned int y = start; y<= stop ; y+=step) { // do linear interpolation - int x = x0 + (x1-x0)*(y-y0)/(y1-y0); + int const dy = static_cast<int>(y)-static_cast<int>(y0); + unsigned int const x = x0 + x_range * dy / y_range; // If the line type is '0', this will clear the pixel // If it is '1' or '2', the pixel will be set @@ -437,7 +440,7 @@ int nrows, int ncols, int *sprite) -{ +{ for (int i = 0; i < nrows; i++) { for (int j = 0 ; j < ncols ; j++) {