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-rw-r--r--src/emu/rendutil.cpp731
1 files changed, 731 insertions, 0 deletions
diff --git a/src/emu/rendutil.cpp b/src/emu/rendutil.cpp
new file mode 100644
index 00000000000..872533583b5
--- /dev/null
+++ b/src/emu/rendutil.cpp
@@ -0,0 +1,731 @@
+// license:BSD-3-Clause
+// copyright-holders:Aaron Giles
+/***************************************************************************
+
+ rendutil.c
+
+ Core rendering utilities.
+***************************************************************************/
+
+#include "emu.h"
+#include "render.h"
+#include "rendutil.h"
+#include "png.h"
+
+
+
+/***************************************************************************
+ FUNCTION PROTOTYPES
+***************************************************************************/
+
+/* utilities */
+static void resample_argb_bitmap_average(UINT32 *dest, UINT32 drowpixels, UINT32 dwidth, UINT32 dheight, const UINT32 *source, UINT32 srowpixels, UINT32 swidth, UINT32 sheight, const render_color &color, UINT32 dx, UINT32 dy);
+static void resample_argb_bitmap_bilinear(UINT32 *dest, UINT32 drowpixels, UINT32 dwidth, UINT32 dheight, const UINT32 *source, UINT32 srowpixels, UINT32 swidth, UINT32 sheight, const render_color &color, UINT32 dx, UINT32 dy);
+static bool copy_png_to_bitmap(bitmap_argb32 &bitmap, const png_info *png);
+static bool copy_png_alpha_to_bitmap(bitmap_argb32 &bitmap, const png_info *png);
+
+
+
+/***************************************************************************
+ RENDER UTILITIES
+***************************************************************************/
+
+/*-------------------------------------------------
+ render_resample_argb_bitmap_hq - perform a high
+ quality resampling of a texture
+-------------------------------------------------*/
+
+void render_resample_argb_bitmap_hq(bitmap_argb32 &dest, bitmap_argb32 &source, const render_color &color)
+{
+ if (dest.width() == 0 || dest.height() == 0)
+ return;
+
+ /* adjust the source base */
+ const UINT32 *sbase = &source.pix32(0);
+
+ /* determine the steppings */
+ UINT32 swidth = source.width();
+ UINT32 sheight = source.height();
+ UINT32 dwidth = dest.width();
+ UINT32 dheight = dest.height();
+ UINT32 dx = (swidth << 12) / dwidth;
+ UINT32 dy = (sheight << 12) / dheight;
+
+ /* if the source is higher res than the target, use full averaging */
+ if (dx > 0x1000 || dy > 0x1000)
+ resample_argb_bitmap_average(&dest.pix(0), dest.rowpixels(), dwidth, dheight, sbase, source.rowpixels(), swidth, sheight, color, dx, dy);
+ else
+ resample_argb_bitmap_bilinear(&dest.pix(0), dest.rowpixels(), dwidth, dheight, sbase, source.rowpixels(), swidth, sheight, color, dx, dy);
+}
+
+
+/*-------------------------------------------------
+ resample_argb_bitmap_average - resample a texture
+ by performing a true weighted average over
+ all contributing pixels
+-------------------------------------------------*/
+
+static void resample_argb_bitmap_average(UINT32 *dest, UINT32 drowpixels, UINT32 dwidth, UINT32 dheight, const UINT32 *source, UINT32 srowpixels, UINT32 swidth, UINT32 sheight, const render_color &color, UINT32 dx, UINT32 dy)
+{
+ UINT64 sumscale = (UINT64)dx * (UINT64)dy;
+ UINT32 r, g, b, a;
+ UINT32 x, y;
+
+ /* precompute premultiplied R/G/B/A factors */
+ r = color.r * color.a * 256.0f;
+ g = color.g * color.a * 256.0f;
+ b = color.b * color.a * 256.0f;
+ a = color.a * 256.0f;
+
+ /* loop over the target vertically */
+ for (y = 0; y < dheight; y++)
+ {
+ UINT32 starty = y * dy;
+
+ /* loop over the target horizontally */
+ for (x = 0; x < dwidth; x++)
+ {
+ UINT64 sumr = 0, sumg = 0, sumb = 0, suma = 0;
+ UINT32 startx = x * dx;
+ UINT32 xchunk, ychunk;
+ UINT32 curx, cury;
+
+ UINT32 yremaining = dy;
+
+ /* accumulate all source pixels that contribute to this pixel */
+ for (cury = starty; yremaining; cury += ychunk)
+ {
+ UINT32 xremaining = dx;
+
+ /* determine the Y contribution, clamping to the amount remaining */
+ ychunk = 0x1000 - (cury & 0xfff);
+ if (ychunk > yremaining)
+ ychunk = yremaining;
+ yremaining -= ychunk;
+
+ /* loop over all source pixels in the X direction */
+ for (curx = startx; xremaining; curx += xchunk)
+ {
+ UINT32 factor;
+
+ /* determine the X contribution, clamping to the amount remaining */
+ xchunk = 0x1000 - (curx & 0xfff);
+ if (xchunk > xremaining)
+ xchunk = xremaining;
+ xremaining -= xchunk;
+
+ /* total contribution = x * y */
+ factor = xchunk * ychunk;
+
+ /* fetch the source pixel */
+ rgb_t pix = source[(cury >> 12) * srowpixels + (curx >> 12)];
+
+ /* accumulate the RGBA values */
+ sumr += factor * pix.r();
+ sumg += factor * pix.g();
+ sumb += factor * pix.b();
+ suma += factor * pix.a();
+ }
+ }
+
+ /* apply scaling */
+ suma = (suma / sumscale) * a / 256;
+ sumr = (sumr / sumscale) * r / 256;
+ sumg = (sumg / sumscale) * g / 256;
+ sumb = (sumb / sumscale) * b / 256;
+
+ /* if we're translucent, add in the destination pixel contribution */
+ if (a < 256)
+ {
+ rgb_t dpix = dest[y * drowpixels + x];
+ suma += dpix.a() * (256 - a);
+ sumr += dpix.r() * (256 - a);
+ sumg += dpix.g() * (256 - a);
+ sumb += dpix.b() * (256 - a);
+ }
+
+ /* store the target pixel, dividing the RGBA values by the overall scale factor */
+ dest[y * drowpixels + x] = rgb_t(suma, sumr, sumg, sumb);
+ }
+ }
+}
+
+
+/*-------------------------------------------------
+ resample_argb_bitmap_bilinear - perform texture
+ sampling via a bilinear filter
+-------------------------------------------------*/
+
+static void resample_argb_bitmap_bilinear(UINT32 *dest, UINT32 drowpixels, UINT32 dwidth, UINT32 dheight, const UINT32 *source, UINT32 srowpixels, UINT32 swidth, UINT32 sheight, const render_color &color, UINT32 dx, UINT32 dy)
+{
+ UINT32 maxx = swidth << 12, maxy = sheight << 12;
+ UINT32 r, g, b, a;
+ UINT32 x, y;
+
+ /* precompute premultiplied R/G/B/A factors */
+ r = color.r * color.a * 256.0f;
+ g = color.g * color.a * 256.0f;
+ b = color.b * color.a * 256.0f;
+ a = color.a * 256.0f;
+
+ /* loop over the target vertically */
+ for (y = 0; y < dheight; y++)
+ {
+ UINT32 starty = y * dy;
+
+ /* loop over the target horizontally */
+ for (x = 0; x < dwidth; x++)
+ {
+ UINT32 startx = x * dx;
+ rgb_t pix0, pix1, pix2, pix3;
+ UINT32 sumr, sumg, sumb, suma;
+ UINT32 nextx, nexty;
+ UINT32 curx, cury;
+ UINT32 factor;
+
+ /* adjust start to the center; note that this math will tend to produce */
+ /* negative results on the first pixel, which is why we clamp below */
+ curx = startx + dx / 2 - 0x800;
+ cury = starty + dy / 2 - 0x800;
+
+ /* compute the neighboring pixel */
+ nextx = curx + 0x1000;
+ nexty = cury + 0x1000;
+
+ /* fetch the four relevant pixels */
+ pix0 = pix1 = pix2 = pix3 = 0;
+ if ((INT32)cury >= 0 && cury < maxy && (INT32)curx >= 0 && curx < maxx)
+ pix0 = source[(cury >> 12) * srowpixels + (curx >> 12)];
+ if ((INT32)cury >= 0 && cury < maxy && (INT32)nextx >= 0 && nextx < maxx)
+ pix1 = source[(cury >> 12) * srowpixels + (nextx >> 12)];
+ if ((INT32)nexty >= 0 && nexty < maxy && (INT32)curx >= 0 && curx < maxx)
+ pix2 = source[(nexty >> 12) * srowpixels + (curx >> 12)];
+ if ((INT32)nexty >= 0 && nexty < maxy && (INT32)nextx >= 0 && nextx < maxx)
+ pix3 = source[(nexty >> 12) * srowpixels + (nextx >> 12)];
+
+ /* compute the x/y scaling factors */
+ curx &= 0xfff;
+ cury &= 0xfff;
+
+ /* contributions from pixel 0 (top,left) */
+ factor = (0x1000 - curx) * (0x1000 - cury);
+ sumr = factor * pix0.r();
+ sumg = factor * pix0.g();
+ sumb = factor * pix0.b();
+ suma = factor * pix0.a();
+
+ /* contributions from pixel 1 (top,right) */
+ factor = curx * (0x1000 - cury);
+ sumr += factor * pix1.r();
+ sumg += factor * pix1.g();
+ sumb += factor * pix1.b();
+ suma += factor * pix1.a();
+
+ /* contributions from pixel 2 (bottom,left) */
+ factor = (0x1000 - curx) * cury;
+ sumr += factor * pix2.r();
+ sumg += factor * pix2.g();
+ sumb += factor * pix2.b();
+ suma += factor * pix2.a();
+
+ /* contributions from pixel 3 (bottom,right) */
+ factor = curx * cury;
+ sumr += factor * pix3.r();
+ sumg += factor * pix3.g();
+ sumb += factor * pix3.b();
+ suma += factor * pix3.a();
+
+ /* apply scaling */
+ suma = (suma >> 24) * a / 256;
+ sumr = (sumr >> 24) * r / 256;
+ sumg = (sumg >> 24) * g / 256;
+ sumb = (sumb >> 24) * b / 256;
+
+ /* if we're translucent, add in the destination pixel contribution */
+ if (a < 256)
+ {
+ rgb_t dpix = dest[y * drowpixels + x];
+ suma += dpix.a() * (256 - a);
+ sumr += dpix.r() * (256 - a);
+ sumg += dpix.g() * (256 - a);
+ sumb += dpix.b() * (256 - a);
+ }
+
+ /* store the target pixel, dividing the RGBA values by the overall scale factor */
+ dest[y * drowpixels + x] = rgb_t(suma, sumr, sumg, sumb);
+ }
+ }
+}
+
+
+/*-------------------------------------------------
+ render_clip_line - clip a line to a rectangle
+-------------------------------------------------*/
+
+int render_clip_line(render_bounds *bounds, const render_bounds *clip)
+{
+ /* loop until we get a final result */
+ while (1)
+ {
+ UINT8 code0 = 0, code1 = 0;
+ UINT8 thiscode;
+ float x, y;
+
+ /* compute Cohen Sutherland bits for first coordinate */
+ if (bounds->y0 > clip->y1)
+ code0 |= 1;
+ if (bounds->y0 < clip->y0)
+ code0 |= 2;
+ if (bounds->x0 > clip->x1)
+ code0 |= 4;
+ if (bounds->x0 < clip->x0)
+ code0 |= 8;
+
+ /* compute Cohen Sutherland bits for second coordinate */
+ if (bounds->y1 > clip->y1)
+ code1 |= 1;
+ if (bounds->y1 < clip->y0)
+ code1 |= 2;
+ if (bounds->x1 > clip->x1)
+ code1 |= 4;
+ if (bounds->x1 < clip->x0)
+ code1 |= 8;
+
+ /* trivial accept: just return FALSE */
+ if ((code0 | code1) == 0)
+ return FALSE;
+
+ /* trivial reject: just return TRUE */
+ if ((code0 & code1) != 0)
+ return TRUE;
+
+ /* fix one of the OOB cases */
+ thiscode = code0 ? code0 : code1;
+
+ /* off the bottom */
+ if (thiscode & 1)
+ {
+ x = bounds->x0 + (bounds->x1 - bounds->x0) * (clip->y1 - bounds->y0) / (bounds->y1 - bounds->y0);
+ y = clip->y1;
+ }
+
+ /* off the top */
+ else if (thiscode & 2)
+ {
+ x = bounds->x0 + (bounds->x1 - bounds->x0) * (clip->y0 - bounds->y0) / (bounds->y1 - bounds->y0);
+ y = clip->y0;
+ }
+
+ /* off the right */
+ else if (thiscode & 4)
+ {
+ y = bounds->y0 + (bounds->y1 - bounds->y0) * (clip->x1 - bounds->x0) / (bounds->x1 - bounds->x0);
+ x = clip->x1;
+ }
+
+ /* off the left */
+ else
+ {
+ y = bounds->y0 + (bounds->y1 - bounds->y0) * (clip->x0 - bounds->x0) / (bounds->x1 - bounds->x0);
+ x = clip->x0;
+ }
+
+ /* fix the appropriate coordinate */
+ if (thiscode == code0)
+ {
+ bounds->x0 = x;
+ bounds->y0 = y;
+ }
+ else
+ {
+ bounds->x1 = x;
+ bounds->y1 = y;
+ }
+ }
+}
+
+
+/*-------------------------------------------------
+ render_clip_quad - clip a quad to a rectangle
+-------------------------------------------------*/
+
+int render_clip_quad(render_bounds *bounds, const render_bounds *clip, render_quad_texuv *texcoords)
+{
+ /* ensure our assumptions about the bounds are correct */
+ assert(bounds->x0 <= bounds->x1);
+ assert(bounds->y0 <= bounds->y1);
+
+ /* trivial reject */
+ if (bounds->y1 < clip->y0)
+ return TRUE;
+ if (bounds->y0 > clip->y1)
+ return TRUE;
+ if (bounds->x1 < clip->x0)
+ return TRUE;
+ if (bounds->x0 > clip->x1)
+ return TRUE;
+
+ /* clip top (x0,y0)-(x1,y1) */
+ if (bounds->y0 < clip->y0)
+ {
+ float frac = (clip->y0 - bounds->y0) / (bounds->y1 - bounds->y0);
+ bounds->y0 = clip->y0;
+ if (texcoords != NULL)
+ {
+ texcoords->tl.u += (texcoords->bl.u - texcoords->tl.u) * frac;
+ texcoords->tl.v += (texcoords->bl.v - texcoords->tl.v) * frac;
+ texcoords->tr.u += (texcoords->br.u - texcoords->tr.u) * frac;
+ texcoords->tr.v += (texcoords->br.v - texcoords->tr.v) * frac;
+ }
+ }
+
+ /* clip bottom (x3,y3)-(x2,y2) */
+ if (bounds->y1 > clip->y1)
+ {
+ float frac = (bounds->y1 - clip->y1) / (bounds->y1 - bounds->y0);
+ bounds->y1 = clip->y1;
+ if (texcoords != NULL)
+ {
+ texcoords->bl.u -= (texcoords->bl.u - texcoords->tl.u) * frac;
+ texcoords->bl.v -= (texcoords->bl.v - texcoords->tl.v) * frac;
+ texcoords->br.u -= (texcoords->br.u - texcoords->tr.u) * frac;
+ texcoords->br.v -= (texcoords->br.v - texcoords->tr.v) * frac;
+ }
+ }
+
+ /* clip left (x0,y0)-(x3,y3) */
+ if (bounds->x0 < clip->x0)
+ {
+ float frac = (clip->x0 - bounds->x0) / (bounds->x1 - bounds->x0);
+ bounds->x0 = clip->x0;
+ if (texcoords != NULL)
+ {
+ texcoords->tl.u += (texcoords->tr.u - texcoords->tl.u) * frac;
+ texcoords->tl.v += (texcoords->tr.v - texcoords->tl.v) * frac;
+ texcoords->bl.u += (texcoords->br.u - texcoords->bl.u) * frac;
+ texcoords->bl.v += (texcoords->br.v - texcoords->bl.v) * frac;
+ }
+ }
+
+ /* clip right (x1,y1)-(x2,y2) */
+ if (bounds->x1 > clip->x1)
+ {
+ float frac = (bounds->x1 - clip->x1) / (bounds->x1 - bounds->x0);
+ bounds->x1 = clip->x1;
+ if (texcoords != NULL)
+ {
+ texcoords->tr.u -= (texcoords->tr.u - texcoords->tl.u) * frac;
+ texcoords->tr.v -= (texcoords->tr.v - texcoords->tl.v) * frac;
+ texcoords->br.u -= (texcoords->br.u - texcoords->bl.u) * frac;
+ texcoords->br.v -= (texcoords->br.v - texcoords->bl.v) * frac;
+ }
+ }
+ return FALSE;
+}
+
+
+/*-------------------------------------------------
+ render_line_to_quad - convert a line and a
+ width to four points
+-------------------------------------------------*/
+
+void render_line_to_quad(const render_bounds *bounds, float width, render_bounds *bounds0, render_bounds *bounds1)
+{
+ render_bounds modbounds = *bounds;
+ float unitx, unity;
+
+ /*
+ High-level logic -- due to math optimizations, this info is lost below.
+
+ Imagine a thick line of width (w), drawn from (p0) to (p1), with a unit
+ vector (u) indicating the direction from (p0) to (p1).
+
+ B C
+ +---------------- ... ------------------+
+ | ^ |
+ | | |
+ | | |
+ * (p0) ------------> (w)| * (p1)
+ | (u) | |
+ | | |
+ | v |
+ +---------------- ... ------------------+
+ A D
+
+ To convert this into a quad, we need to compute the four points A, B, C
+ and D.
+
+ Starting with point A. We first multiply the unit vector by 0.5w and then
+ rotate the result 90 degrees. Thus, we have:
+
+ A.x = p0.x + 0.5 * w * u.x * cos(90) - 0.5 * w * u.y * sin(90)
+ A.y = p0.y + 0.5 * w * u.x * sin(90) + 0.5 * w * u.y * cos(90)
+
+ Conveniently, sin(90) = 1, and cos(90) = 0, so this simplifies to:
+
+ A.x = p0.x - 0.5 * w * u.y
+ A.y = p0.y + 0.5 * w * u.x
+
+ Working clockwise around the polygon, the same fallout happens all around as
+ we rotate the unit vector by -90 (B), -90 (C), and 90 (D) degrees:
+
+ B.x = p0.x + 0.5 * w * u.y
+ B.y = p0.y - 0.5 * w * u.x
+
+ C.x = p1.x - 0.5 * w * u.y
+ C.y = p1.y + 0.5 * w * u.x
+
+ D.x = p1.x + 0.5 * w * u.y
+ D.y = p1.y - 0.5 * w * u.x
+ */
+
+ /* we only care about the half-width */
+ width *= 0.5f;
+
+ /* compute a vector from point 0 to point 1 */
+ unitx = modbounds.x1 - modbounds.x0;
+ unity = modbounds.y1 - modbounds.y0;
+
+ /* points just use a +1/+1 unit vector; this gives a nice diamond pattern */
+ if (unitx == 0 && unity == 0)
+ {
+ unitx = unity = 0.70710678f * width;
+ modbounds.x0 -= 0.5f * unitx;
+ modbounds.y0 -= 0.5f * unity;
+ modbounds.x1 += 0.5f * unitx;
+ modbounds.y1 += 0.5f * unity;
+ }
+
+ /* lines need to be divided by their length */
+ else
+ {
+ /* prescale unitx and unity by the half-width */
+ float invlength = width / sqrtf(unitx * unitx + unity * unity);
+ unitx *= invlength;
+ unity *= invlength;
+ }
+
+ /* rotate the unit vector by 90 degrees and add to point 0 */
+ bounds0->x0 = modbounds.x0 - unity;
+ bounds0->y0 = modbounds.y0 + unitx;
+
+ /* rotate the unit vector by -90 degrees and add to point 0 */
+ bounds0->x1 = modbounds.x0 + unity;
+ bounds0->y1 = modbounds.y0 - unitx;
+
+ /* rotate the unit vector by 90 degrees and add to point 1 */
+ bounds1->x0 = modbounds.x1 - unity;
+ bounds1->y0 = modbounds.y1 + unitx;
+
+ /* rotate the unit vector by -09 degrees and add to point 1 */
+ bounds1->x1 = modbounds.x1 + unity;
+ bounds1->y1 = modbounds.y1 - unitx;
+}
+
+
+/*-------------------------------------------------
+ render_load_png - load a PNG file into a
+ bitmap
+-------------------------------------------------*/
+
+bool render_load_png(bitmap_argb32 &bitmap, emu_file &file, const char *dirname, const char *filename, bool load_as_alpha_to_existing)
+{
+ // deallocate if we're not overlaying alpha
+ if (!load_as_alpha_to_existing)
+ bitmap.reset();
+
+ // open the file
+ std::string fname;
+ if (dirname == NULL)
+ fname.assign(filename);
+ else
+ fname.assign(dirname).append(PATH_SEPARATOR).append(filename);
+ file_error filerr = file.open(fname.c_str());
+ if (filerr != FILERR_NONE)
+ return false;
+
+ // read the PNG data
+ png_info png;
+ png_error result = png_read_file(file, &png);
+ file.close();
+ if (result != PNGERR_NONE)
+ return false;
+
+ // verify we can handle this PNG
+ if (png.bit_depth > 8)
+ {
+ osd_printf_error("%s: Unsupported bit depth %d (8 bit max)\n", filename, png.bit_depth);
+ png_free(&png);
+ return false;
+ }
+ if (png.interlace_method != 0)
+ {
+ osd_printf_error("%s: Interlace unsupported\n", filename);
+ png_free(&png);
+ return false;
+ }
+ if (png.color_type != 0 && png.color_type != 3 && png.color_type != 2 && png.color_type != 6)
+ {
+ osd_printf_error("%s: Unsupported color type %d\n", filename, png.color_type);
+ png_free(&png);
+ return false;
+ }
+
+ // if less than 8 bits, upsample
+ png_expand_buffer_8bit(&png);
+
+ // non-alpha case
+ bool hasalpha = false;
+ if (!load_as_alpha_to_existing)
+ {
+ bitmap.allocate(png.width, png.height);
+ hasalpha = copy_png_to_bitmap(bitmap, &png);
+ }
+
+ // alpha case
+ else if (png.width == bitmap.width() && png.height == bitmap.height())
+ hasalpha = copy_png_alpha_to_bitmap(bitmap, &png);
+
+ // free PNG data
+ png_free(&png);
+ return hasalpha;
+}
+
+
+/*-------------------------------------------------
+ copy_png_to_bitmap - copy the PNG data to a
+ bitmap
+-------------------------------------------------*/
+
+static bool copy_png_to_bitmap(bitmap_argb32 &bitmap, const png_info *png)
+{
+ UINT8 accumalpha = 0xff;
+ UINT8 *src;
+ int x, y;
+
+ /* handle 8bpp palettized case */
+ if (png->color_type == 3)
+ {
+ /* loop over width/height */
+ src = png->image;
+ for (y = 0; y < png->height; y++)
+ for (x = 0; x < png->width; x++, src++)
+ {
+ /* determine alpha and expand to 32bpp */
+ UINT8 alpha = (*src < png->num_trans) ? png->trans[*src] : 0xff;
+ accumalpha &= alpha;
+ bitmap.pix32(y, x) = rgb_t(alpha, png->palette[*src * 3], png->palette[*src * 3 + 1], png->palette[*src * 3 + 2]);
+ }
+ }
+
+ /* handle 8bpp grayscale case */
+ else if (png->color_type == 0)
+ {
+ /* loop over width/height */
+ src = png->image;
+ for (y = 0; y < png->height; y++)
+ for (x = 0; x < png->width; x++, src++)
+ bitmap.pix32(y, x) = rgb_t(0xff, *src, *src, *src);
+ }
+
+ /* handle 32bpp non-alpha case */
+ else if (png->color_type == 2)
+ {
+ /* loop over width/height */
+ src = png->image;
+ for (y = 0; y < png->height; y++)
+ for (x = 0; x < png->width; x++, src += 3)
+ bitmap.pix32(y, x) = rgb_t(0xff, src[0], src[1], src[2]);
+ }
+
+ /* handle 32bpp alpha case */
+ else
+ {
+ /* loop over width/height */
+ src = png->image;
+ for (y = 0; y < png->height; y++)
+ for (x = 0; x < png->width; x++, src += 4)
+ {
+ accumalpha &= src[3];
+ bitmap.pix32(y, x) = rgb_t(src[3], src[0], src[1], src[2]);
+ }
+ }
+
+ /* set the hasalpha flag */
+ return (accumalpha != 0xff);
+}
+
+
+/*-------------------------------------------------
+ copy_png_alpha_to_bitmap - copy the PNG data
+ to the alpha channel of a bitmap
+-------------------------------------------------*/
+
+static bool copy_png_alpha_to_bitmap(bitmap_argb32 &bitmap, const png_info *png)
+{
+ UINT8 accumalpha = 0xff;
+ UINT8 *src;
+ int x, y;
+
+ /* handle 8bpp palettized case */
+ if (png->color_type == 3)
+ {
+ /* loop over width/height */
+ src = png->image;
+ for (y = 0; y < png->height; y++)
+ for (x = 0; x < png->width; x++, src++)
+ {
+ rgb_t pixel = bitmap.pix32(y, x);
+ UINT8 alpha = rgb_t(png->palette[*src * 3], png->palette[*src * 3 + 1], png->palette[*src * 3 + 2]).brightness();
+ accumalpha &= alpha;
+ bitmap.pix32(y, x) = rgb_t(alpha, pixel.r(), pixel.g(), pixel.b());
+ }
+ }
+
+ /* handle 8bpp grayscale case */
+ else if (png->color_type == 0)
+ {
+ /* loop over width/height */
+ src = png->image;
+ for (y = 0; y < png->height; y++)
+ for (x = 0; x < png->width; x++, src++)
+ {
+ rgb_t pixel = bitmap.pix32(y, x);
+ accumalpha &= *src;
+ bitmap.pix32(y, x) = rgb_t(*src, pixel.r(), pixel.g(), pixel.b());
+ }
+ }
+
+ /* handle 32bpp non-alpha case */
+ else if (png->color_type == 2)
+ {
+ /* loop over width/height */
+ src = png->image;
+ for (y = 0; y < png->height; y++)
+ for (x = 0; x < png->width; x++, src += 3)
+ {
+ rgb_t pixel = bitmap.pix32(y, x);
+ UINT8 alpha = rgb_t(src[0], src[1], src[2]).brightness();
+ accumalpha &= alpha;
+ bitmap.pix32(y, x) = rgb_t(alpha, pixel.r(), pixel.g(), pixel.b());
+ }
+ }
+
+ /* handle 32bpp alpha case */
+ else
+ {
+ /* loop over width/height */
+ src = png->image;
+ for (y = 0; y < png->height; y++)
+ for (x = 0; x < png->width; x++, src += 4)
+ {
+ rgb_t pixel = bitmap.pix32(y, x);
+ UINT8 alpha = rgb_t(src[0], src[1], src[2]).brightness();
+ accumalpha &= alpha;
+ bitmap.pix32(y, x) = rgb_t(alpha, pixel.r(), pixel.g(), pixel.b());
+ }
+ }
+
+ /* set the hasalpha flag */
+ return (accumalpha != 0xff);
+}