[Piglit] [PATCH 1/2] util: provide way to read a texture in ES compatible way

[Tapani Pälli]

Implementation supports GL_TEXTURE_2D, GL_TEXTURE_2D_ARRAY
and affects following functions:

   - piglit_probe_texel_rect_rgba
   - piglit_probe_texel_volume_rgba

Signed-off-by: Tapani Pälli <tapani.pa...@intel.com>
---
 tests/util/piglit-util-gl.c | 109 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 105 insertions(+), 4 deletions(-)

diff --git a/tests/util/piglit-util-gl.c b/tests/util/piglit-util-gl.c
index 2443be03e..f6a83e717 100644
--- a/tests/util/piglit-util-gl.c
+++ b/tests/util/piglit-util-gl.c
@@ -1882,6 +1882,99 @@ piglit_probe_image_ubyte(int x, int y, int w, int h, 
GLenum format,
        return 1;
 }
 
+static GLuint
+create_fbo_from_texture(GLenum target, GLint texture, GLint level, GLint layer)
+{
+       GLuint fbo;
+
+       glGenFramebuffers(1, &fbo);
+       glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+
+       if (layer > 0) {
+               glFramebufferTextureLayer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                                         texture, level, layer);
+       } else {
+               glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                                      target, texture, level);
+       }
+
+       assert(glCheckFramebufferStatus(GL_FRAMEBUFFER) ==
+              GL_FRAMEBUFFER_COMPLETE);
+       return fbo;
+}
+
+static GLenum
+binding_from_target(GLenum target)
+{
+       switch (target) {
+       case GL_TEXTURE_2D:
+               return GL_TEXTURE_BINDING_2D;
+       case GL_TEXTURE_2D_ARRAY:
+               return GL_TEXTURE_BINDING_2D_ARRAY;
+       default:
+               fprintf(stderr, "%s: unsupported target 0x%x\n",
+                       __func__, target);
+               return 0;
+       }
+}
+
+/**
+ * Read texels in OpenGL ES compatible way.
+ *
+ * Currently bound texture is attached to a framebuffer object and
+ * contents are read using glReadPixels. Supported targets are
+ * GL_TEXTURE_2D, GL_TEXTURE_2D_ARRAY.
+ */
+static GLfloat *
+read_texture(int target, int level, int x, int y, int layer, int w, int h)
+{
+       GLint width, height, depth;
+       GLint current_read_fbo, current_draw_fbo, current_texture;
+       GLenum binding = binding_from_target(target);
+       unsigned char *buf;
+       GLfloat *buffer;
+       unsigned offset;
+
+       assert(binding != 0);
+
+       glGetIntegerv(binding, &current_texture);
+       glGetIntegerv(GL_READ_FRAMEBUFFER_BINDING, &current_read_fbo);
+       glGetIntegerv(GL_DRAW_FRAMEBUFFER_BINDING, &current_draw_fbo);
+
+       assert(target == GL_TEXTURE_2D || target == GL_TEXTURE_2D_ARRAY);
+
+       glGetTexLevelParameteriv(target, level, GL_TEXTURE_WIDTH, &width);
+       glGetTexLevelParameteriv(target, level, GL_TEXTURE_HEIGHT, &height);
+       glGetTexLevelParameteriv(target, level, GL_TEXTURE_DEPTH, &depth);
+
+       buffer = malloc(width * height * depth * 4 * sizeof(GLfloat));
+       buf = malloc(width * height * depth * 4 * sizeof(unsigned char));
+
+       GLuint fbo =
+               create_fbo_from_texture(target, current_texture, level, layer);
+       assert(fbo != 0);
+
+       /* Offset to the layer we are expected to read. */
+       offset = layer * (width * height * 4);
+
+       glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE,
+                    buf + offset);
+
+       for (unsigned k = offset; k < offset + width * height * 4; k++)
+               buffer[k] = ((float) buf[k]) / 255.0;
+
+       free(buf);
+
+       glDeleteFramebuffers(1, &fbo);
+
+       /* Restore FBO state. */
+       glBindFramebuffer(GL_READ_FRAMEBUFFER, current_read_fbo);
+       glBindFramebuffer(GL_DRAW_FRAMEBUFFER, current_draw_fbo);
+
+       return buffer;
+}
+
+
 /**
  * Read a texel rectangle from the given location and compare its RGB value to
  * the given expected values.
@@ -1957,9 +2050,13 @@ int piglit_probe_texel_rect_rgba(int target, int level, 
int x, int y,
 
        glGetTexLevelParameteriv(target, level, GL_TEXTURE_WIDTH, &width);
        glGetTexLevelParameteriv(target, level, GL_TEXTURE_HEIGHT, &height);
-       buffer = malloc(width * height * 4 * sizeof(GLfloat));
 
-       glGetTexImage(target, level, GL_RGBA, GL_FLOAT, buffer);
+       if (target == GL_TEXTURE_2D) {
+               buffer = read_texture(target, level, x, y, 0, w, h);
+       } else {
+               buffer = malloc(width * height * 4 * sizeof(GLfloat));
+               glGetTexImage(target, level, GL_RGBA, GL_FLOAT, buffer);
+       }
 
        assert(x >= 0);
        assert(y >= 0);
@@ -2021,9 +2118,13 @@ int piglit_probe_texel_volume_rgba(int target, int 
level, int x, int y, int z,
        glGetTexLevelParameteriv(target, level, GL_TEXTURE_WIDTH, &width);
        glGetTexLevelParameteriv(target, level, GL_TEXTURE_HEIGHT, &height);
        glGetTexLevelParameteriv(target, level, GL_TEXTURE_DEPTH, &depth);
-       buffer = malloc(width * height * depth * 4 * sizeof(GLfloat));
 
-       glGetTexImage(target, level, GL_RGBA, GL_FLOAT, buffer);
+       if (target == GL_TEXTURE_2D || GL_TEXTURE_2D_ARRAY) {
+               buffer = read_texture(target, level, x, y, z, w, h);
+        } else {
+               buffer = malloc(width * height * depth * 4 * sizeof(GLfloat));
+               glGetTexImage(target, level, GL_RGBA, GL_FLOAT, buffer);
+       }
 
        assert(x >= 0);
        assert(y >= 0);
-- 
2.14.3

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