s_texfilter.c

Mesa is an open-source implementation of the OpenGL specification - a system for rendering interacti

sample_linear_1d( GLcontext *ctx,
                  const struct gl_texture_object *tObj, GLuint n,
                  const GLfloat texcoords[][4], const GLfloat lambda[],
                  GLchan rgba[][4] )
{
   GLuint i;
   struct gl_texture_image *image = tObj->Image[0][tObj->BaseLevel];
   (void) lambda;
   for (i=0;i<n;i++) {
      sample_1d_linear(ctx, tObj, image, texcoords[i], rgba[i]);
   }
}


/*
 * Given an (s) texture coordinate and lambda (level of detail) value,
 * return a texture sample.
 *
 */
static void
sample_lambda_1d( GLcontext *ctx,
                  const struct gl_texture_object *tObj, GLuint n,
                  const GLfloat texcoords[][4],
                  const GLfloat lambda[], GLchan rgba[][4] )
{
   GLuint minStart, minEnd;  /* texels with minification */
   GLuint magStart, magEnd;  /* texels with magnification */
   GLuint i;

   ASSERT(lambda != NULL);
   compute_min_mag_ranges(tObj, n, lambda,
                          &minStart, &minEnd, &magStart, &magEnd);

   if (minStart < minEnd) {
      /* do the minified texels */
      const GLuint m = minEnd - minStart;
      switch (tObj->MinFilter) {
      case GL_NEAREST:
         for (i = minStart; i < minEnd; i++)
            sample_1d_nearest(ctx, tObj, tObj->Image[0][tObj->BaseLevel],
                              texcoords[i], rgba[i]);
         break;
      case GL_LINEAR:
         for (i = minStart; i < minEnd; i++)
            sample_1d_linear(ctx, tObj, tObj->Image[0][tObj->BaseLevel],
                             texcoords[i], rgba[i]);
         break;
      case GL_NEAREST_MIPMAP_NEAREST:
         sample_1d_nearest_mipmap_nearest(ctx, tObj, m, texcoords + minStart,
                                          lambda + minStart, rgba + minStart);
         break;
      case GL_LINEAR_MIPMAP_NEAREST:
         sample_1d_linear_mipmap_nearest(ctx, tObj, m, texcoords + minStart,
                                         lambda + minStart, rgba + minStart);
         break;
      case GL_NEAREST_MIPMAP_LINEAR:
         sample_1d_nearest_mipmap_linear(ctx, tObj, m, texcoords + minStart,
                                         lambda + minStart, rgba + minStart);
         break;
      case GL_LINEAR_MIPMAP_LINEAR:
         sample_1d_linear_mipmap_linear(ctx, tObj, m, texcoords + minStart,
                                        lambda + minStart, rgba + minStart);
         break;
      default:
         _mesa_problem(ctx, "Bad min filter in sample_1d_texture");
         return;
      }
   }

   if (magStart < magEnd) {
      /* do the magnified texels */
      switch (tObj->MagFilter) {
      case GL_NEAREST:
         for (i = magStart; i < magEnd; i++)
            sample_1d_nearest(ctx, tObj, tObj->Image[0][tObj->BaseLevel],
                              texcoords[i], rgba[i]);
         break;
      case GL_LINEAR:
         for (i = magStart; i < magEnd; i++)
            sample_1d_linear(ctx, tObj, tObj->Image[0][tObj->BaseLevel],
                             texcoords[i], rgba[i]);
         break;
      default:
         _mesa_problem(ctx, "Bad mag filter in sample_1d_texture");
         return;
      }
   }
}


/**********************************************************************/
/*                    2-D Texture Sampling Functions                  */
/**********************************************************************/


/*
 * Return the texture sample for coordinate (s,t) using GL_NEAREST filter.
 */
static INLINE void
sample_2d_nearest(GLcontext *ctx,
                  const struct gl_texture_object *tObj,
                  const struct gl_texture_image *img,
                  const GLfloat texcoord[4],
                  GLchan rgba[])
{
   const GLint width = img->Width2;    /* without border, power of two */
   const GLint height = img->Height2;  /* without border, power of two */
   GLint i, j;
   (void) ctx;

   COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapS, texcoord[0], width,  i);
   COMPUTE_NEAREST_TEXEL_LOCATION(tObj->WrapT, texcoord[1], height, j);

   /* skip over the border, if any */
   i += img->Border;
   j += img->Border;

   if (i < 0 || i >= (GLint) img->Width || j < 0 || j >= (GLint) img->Height) {
      /* Need this test for GL_CLAMP_TO_BORDER mode */
      COPY_CHAN4(rgba, tObj->_BorderChan);
   }
   else {
      img->FetchTexelc(img, i, j, 0, rgba);
   }
}



/**
 * Return the texture sample for coordinate (s,t) using GL_LINEAR filter.
 * New sampling code contributed by Lynn Quam <[e-mail]>.
 */
static INLINE void
sample_2d_linear(GLcontext *ctx,
                 const struct gl_texture_object *tObj,
                 const struct gl_texture_image *img,
                 const GLfloat texcoord[4],
                 GLchan rgba[])
{
   const GLint width = img->Width2;
   const GLint height = img->Height2;
   GLint i0, j0, i1, j1;
   GLbitfield useBorderColor = 0x0;
   GLfloat u, v;
   GLfloat a, b;
   GLchan t00[4], t10[4], t01[4], t11[4]; /* sampled texel colors */

   COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapS, texcoord[0], u, width,  i0, i1);
   COMPUTE_LINEAR_TEXEL_LOCATIONS(tObj->WrapT, texcoord[1], v, height, j0, j1);

   if (img->Border) {
      i0 += img->Border;
      i1 += img->Border;
      j0 += img->Border;
      j1 += img->Border;
   }
   else {
      if (i0 < 0 || i0 >= width)   useBorderColor |= I0BIT;
      if (i1 < 0 || i1 >= width)   useBorderColor |= I1BIT;
      if (j0 < 0 || j0 >= height)  useBorderColor |= J0BIT;
      if (j1 < 0 || j1 >= height)  useBorderColor |= J1BIT;
   }

   /* fetch four texel colors */
   if (useBorderColor & (I0BIT | J0BIT)) {
      COPY_CHAN4(t00, tObj->_BorderChan);
   }
   else {
      img->FetchTexelc(img, i0, j0, 0, t00);
   }
   if (useBorderColor & (I1BIT | J0BIT)) {
      COPY_CHAN4(t10, tObj->_BorderChan);
   }
   else {
      img->FetchTexelc(img, i1, j0, 0, t10);
   }
   if (useBorderColor & (I0BIT | J1BIT)) {
      COPY_CHAN4(t01, tObj->_BorderChan);
   }
   else {
      img->FetchTexelc(img, i0, j1, 0, t01);
   }
   if (useBorderColor & (I1BIT | J1BIT)) {
      COPY_CHAN4(t11, tObj->_BorderChan);
   }
   else {
      img->FetchTexelc(img, i1, j1, 0, t11);
   }

   a = FRAC(u);
   b = FRAC(v);
   lerp_rgba_2d(rgba, a, b, t00, t10, t01, t11);
}


/*
 * As above, but we know WRAP_S == REPEAT and WRAP_T == REPEAT.
 * We don't have to worry about the texture border.
 */
static INLINE void
sample_2d_linear_repeat(GLcontext *ctx,
                        const struct gl_texture_object *tObj,
                        const struct gl_texture_image *img,
                        const GLfloat texcoord[4],
                        GLchan rgba[])
{
   const GLint width = img->Width2;
   const GLint height = img->Height2;
   GLint i0, j0, i1, j1;
   GLfloat u, v;
   GLfloat a, b;
   GLchan t00[4], t10[4], t01[4], t11[4]; /* sampled texel colors */

   (void) ctx;

   ASSERT(tObj->WrapS == GL_REPEAT);
   ASSERT(tObj->WrapT == GL_REPEAT);
   ASSERT(img->Border == 0);
   ASSERT(img->TexFormat->BaseFormat != GL_COLOR_INDEX);
   ASSERT(img->_IsPowerOfTwo);

   COMPUTE_LINEAR_REPEAT_TEXEL_LOCATION(texcoord[0], u, width,  i0, i1);
   COMPUTE_LINEAR_REPEAT_TEXEL_LOCATION(texcoord[1], v, height, j0, j1);

   img->FetchTexelc(img, i0, j0, 0, t00);
   img->FetchTexelc(img, i1, j0, 0, t10);
   img->FetchTexelc(img, i0, j1, 0, t01);
   img->FetchTexelc(img, i1, j1, 0, t11);

   a = FRAC(u);
   b = FRAC(v);
   lerp_rgba_2d(rgba, a, b, t00, t10, t01, t11);
}



static void
sample_2d_nearest_mipmap_nearest(GLcontext *ctx,
                                 const struct gl_texture_object *tObj,
                                 GLuint n, const GLfloat texcoord[][4],
                                 const GLfloat lambda[], GLchan rgba[][4])
{
   GLuint i;
   for (i = 0; i < n; i++) {
      GLint level = nearest_mipmap_level(tObj, lambda[i]);
      sample_2d_nearest(ctx, tObj, tObj->Image[0][level], texcoord[i], rgba[i]);
   }
}



static void
sample_2d_linear_mipmap_nearest(GLcontext *ctx,
                                const struct gl_texture_object *tObj,
                                GLuint n, const GLfloat texcoord[][4],
                                const GLfloat lambda[], GLchan rgba[][4])
{
   GLuint i;
   ASSERT(lambda != NULL);
   for (i = 0; i < n; i++) {
      GLint level = nearest_mipmap_level(tObj, lambda[i]);
      sample_2d_linear(ctx, tObj, tObj->Image[0][level], texcoord[i], rgba[i]);
   }
}



static void
sample_2d_nearest_mipmap_linear(GLcontext *ctx,
                                const struct gl_texture_object *tObj,
                                GLuint n, const GLfloat texcoord[][4],
                                const GLfloat lambda[], GLchan rgba[][4])
{
   GLuint i;
   ASSERT(lambda != NULL);
   for (i = 0; i < n; i++) {
      GLint level = linear_mipmap_level(tObj, lambda[i]);
      if (level >= tObj->_MaxLevel) {
         sample_2d_nearest(ctx, tObj, tObj->Image[0][tObj->_MaxLevel],
                           texcoord[i], rgba[i]);
      }
      else {
         GLchan t0[4], t1[4];  /* texels */
         const GLfloat f = FRAC(lambda[i]);
         sample_2d_nearest(ctx, tObj, tObj->Image[0][level  ], texcoord[i], t0);
         sample_2d_nearest(ctx, tObj, tObj->Image[0][level+1], texcoord[i], t1);
         lerp_rgba(rgba[i], f, t0, t1);
      }
   }
}



/* Trilinear filtering */
static void
sample_2d_linear_mipmap_linear( GLcontext *ctx,
                                const struct gl_texture_object *tObj,
                                GLuint n, const GLfloat texcoord[][4],
                                const GLfloat lambda[], GLchan rgba[][4] )
{
   GLuint i;
   ASSERT(lambda != NULL);
   for (i = 0; i < n; i++) {
      GLint level = linear_mipmap_level(tObj, lambda[i]);
      if (level >= tObj->_MaxLevel) {
         sample_2d_linear(ctx, tObj, tObj->Image[0][tObj->_MaxLevel],
                          texcoord[i], rgba[i]);
      }
      else {
         GLchan t0[4], t1[4];  /* texels */
         const GLfloat f = FRAC(lambda[i]);
         sample_2d_linear(ctx, tObj, tObj->Image[0][level  ], texcoord[i], t0);
         sample_2d_linear(ctx, tObj, tObj->Image[0][level+1], texcoord[i], t1);
         lerp_rgba(rgba[i], f, t0, t1);
      }
   }
}


static void
sample_2d_linear_mipmap_linear_repeat( GLcontext *ctx,
                                       const struct gl_texture_object *tObj,
                                       GLuint n, const GLfloat texcoord[][4],
                                       const GLfloat lambda[], GLchan rgba[][4] )
{
   GLuint i;
   ASSERT(lambda != NULL);
   ASSERT(tObj->WrapS == GL_REPEAT);
   ASSERT(tObj->WrapT == GL_REPEAT);
   for (i = 0; i < n; i++) {
      GLint level = linear_mipmap_level(tObj, lambda[i]);
      if (level >= tObj->_MaxLevel) {
         sample_2d_linear_repeat(ctx, tObj, tObj->Image[0][tObj->_MaxLevel],
                                 texcoord[i], rgba[i]);
      }
      else {
         GLchan t0[4], t1[4];  /* texels */
         const GLfloat f = FRAC(lambda[i]);
         sample_2d_linear_repeat(ctx, tObj, tObj->Image[0][level  ], texcoord[i], t0);
         sample_2d_linear_repeat(ctx, tObj, tObj->Image[0][level+1], texcoord[i], t1);
         lerp_rgba(rgba[i], f, t0, t1);
      }
   }
}


static void
sample_nearest_2d( GLcontext *ctx,
                   const struct gl_texture_object *tObj, GLuint n,
                   const GLfloat texcoords[][4],
                   const GLfloat lambda[], GLchan rgba[][4] )
{
   GLuint i;
   struct gl_texture_image *image = tObj->Image[0][tObj->BaseLevel];
   (void) lambda;
   for (i=0;i<n;i++) {
      sample_2d_nearest(ctx, tObj, image, texcoords[i], rgba[i]);
   }
}



static void
sample_linear_2d( GLcontext *ctx,
                  const struct gl_texture_object *tObj, GLuint n,
                  const GLfloat texcoords[][4],
                  const GLfloat lambda[], GLchan rgba[][4] )
{
   GLuint i;
   struct gl_texture_image *image = tObj->Image[0][tObj->BaseLevel];
   (void) lambda;
   if (tObj->WrapS == GL_REPEAT &&
       tObj->WrapT == GL_REPEAT &&
       image->_IsPowerOfTwo &&
       image->Border == 0) {
      for (i=0;i<n;i++) {
         sample_2d_linear_repeat(ctx, tObj, image, texcoords[i], rgba[i]);
      }
   }
   else {
      for (i=0;i<n;i++) {
         sample_2d_linear(ctx, tObj, image, texcoords[i], rgba[i]);
      }
   }
}


/*
 * Optimized 2-D texture sampling:
 *    S and T wrap mode == GL_REPEAT
 *    GL_NEAREST min/mag filter
 *    No border, 
 *    RowStride == Width,
 *    Format = GL_RGB
 */
static void
opt_sample_rgb_2d( GLcontext *ctx,
                   const struct gl_texture_object *tObj,
                   GLuint n, const GLfloat texcoords[][4],
                   const GLfloat lambda[], GLchan rgba[][4] )
{
   const struct gl_texture_image *img = tObj->Image[0][tObj->BaseLevel];
   const GLfloat width = (GLfloat) img->Width;
   const GLfloat height = (GLfloat) img->Height;
   const GLint colMask = img->Width - 1;
   const GLint rowMask = img->Height - 1;
   const GLint shift = img->WidthLog2;
   GLuint k;
   (void) ctx;
   (void) lambda;
   ASSERT(tObj->WrapS==GL_REPEAT);