mirror of
https://github.com/isometimes/rpi4-osdev
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53 lines
2 KiB
C
53 lines
2 KiB
C
#include "wgt.h"
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#define fastcopy memcpy
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void wskew (short x, short y, block image, short degrees)
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{
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float newx, offs, slope;
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long lnewx, lslope;
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/* long values converted from floats (speed up) */
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short ctr; /* y ctr */
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short hgt, wid, display, shx, of2;
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short onewx;
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hgt = wgetblockheight (image); /* Find height of block */
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wid = wgetblockwidth (image); /* Find width of block */
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slope = (float)degrees / 45; /* Calculate slope of new image */
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offs = ((float)hgt / 2)*slope; /* Find distance to shift horiz. */
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newx = (float)x + offs; /* Calculate new x position */
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onewx = newx; /* Store it as integer for clipping */
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lnewx = (float)newx * 2000; /* Convert floating pt to long int */
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lslope = (float)slope * 2000; /* Convert floating pt to long int */
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/* Draw each row of image */
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for (ctr = y; ctr < y + hgt - 1; ctr++)
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{
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if (onewx + wid > bx) display = bx + 1 - onewx;
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/* Clip width */
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else display = wid;
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if (onewx < tx) /* See if image overlaps left clip */
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{
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of2 = tx - onewx; /* Find offset into bitmap */
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shx = tx; /* Set to draw starting here */
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display = display - of2; /* New width to draw */
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}
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else
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{
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shx = onewx; /* X value is fine */
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of2 = 0; /* Use entire bitmap */
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}
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/* If width to display >0, and <= original width, and
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we are within top and bottom Y clipping boundaries:
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Copy row of bitmap to visual screen, using DISPLAY contiguous
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bytes.
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*/
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if ((display > 0) & (display <= wid) & (ctr >= ty) & (ctr <= by))
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fastcopy (&abuf[(ctr)*WGT_SYS.xres + shx], &image[(ctr - y)*wid + 2
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+ of2], display);
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lnewx = lnewx - lslope;
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/* Find X position after shifting next row */
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onewx = lnewx / 2000;
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/* Calculate integer value from long int */
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}
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}
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