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/* -*- c -*- */
#version 330
// must match VBO_location_image in GL_image_display.c
layout (location = 0) in vec2 vertex;
out vec2 tex_xy_geometry;
uniform vec2 aspect;
uniform vec2 center01;
uniform float visible_width01;
uniform int flip_x, flip_y, flip_y_data_is_upside_down;
void main(void)
{
// vertex is in [0,1]: the image we're displaying, possibly flipped
//
// tex_xy_geometry is in [0,1]: the image we're displaying
// gl_Position is in [-1,1]: this is the viewport
// The logic of flip_x is as expected. The logic of flip_y is inverted
// because OpenGL stores images that way.
// The caller says when to flip stuff. Generally if given a raw buffer I
// assume it's already rightside-up. But when loading an image using
// FreeImage_Load() I assume it's upside down, since that's what
// libfreeimage does
if(flip_x == 0)
tex_xy_geometry.x = vertex.x;
else
tex_xy_geometry.x = 1.0 - vertex.x;
// flip_y xor !flip_y_data_is_upside_down
if((flip_y!=0 && flip_y_data_is_upside_down==0) ||
(flip_y==0 && flip_y_data_is_upside_down!=0))
// input image has the upside-down orientation, but that's what opengl
// wants, so I'm good
tex_xy_geometry.y = vertex.y;
else
// input image it rightside-up, but opengl wants it to be upside-down,
// so I flip it
tex_xy_geometry.y = 1.0 - vertex.y;
gl_Position = vec4( (vertex - center01) / visible_width01 * 2.,
0, 1 );
gl_Position.x *= aspect.x;
gl_Position.y *= aspect.y;
}
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