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Rendering and Cropping/Stretching an Image Using Slick/OpenGL (using getSubImage)

I'm trying to recreate a shadow effect on some 2D sprites in a project using Slick. To do this, I'm recolouring a copy of the sprite and stretching it using Slick OpenGL using this method:
public static void getStretched(Shape shape, Image image) {
TextureImpl.bindNone();
image.getTexture().bind();
SGL GL = Renderer.get();
GL.glEnable(SGL.GL_TEXTURE_2D);
GL.glBegin(SGL.GL_QUADS);
//topleft
GL.glTexCoord2f(0f, 0f);
GL.glVertex2f(shape.getPoints()[0], shape.getPoints()[1]);
//topright
GL.glTexCoord2f(0.5f, 0f);
GL.glVertex2f(shape.getPoints()[2], shape.getPoints()[3]);
//bottom right
GL.glTexCoord2f(1f, 1f);
GL.glVertex2f(shape.getPoints()[4], shape.getPoints()[5]);
//btoom left
GL.glTexCoord2f(0.5f, 1f);
GL.glVertex2f(shape.getPoints()[6], shape.getPoints()[7]);
GL.glEnd();
GL.glDisable(SGL.GL_TEXTURE_2D);
TextureImpl.bindNone();
}
This gives the almost the desired effect, aside from the fact that the image is cropped a bit.
This becomes more extreme for higher distortions
I'm new to using OpenGL, so some help regarding how to fix this would be great.
Furthermore, if I feed an image into the method that was obtained using getSubImage, OpenGL renders the original image, rather than the sub image.
I'm unsure as to why this happens, as the sprite itself is taken from a spritesheet using getSubImage and has no problem rendering.
Help would be greatly appreciated!

I'm recolouring a copy of the sprite and stretching it
The issue is that you stretch the texture coordinates, but the region which is covered by the sprite stays the same. If the shadow exceeds the the region which is covered by the quad primitive, then it is cropped.
You have to "stretch" the vertex coordinates rather than the texture coordinates. Define a rhombic geometry for the shadow and wrap the texture on it:
float distortionX = ...;
GL.glEnable(SGL.GL_TEXTURE_2D);
GL.glBegin(SGL.GL_QUADS);
//topleft
GL.glTexCoord2f(0f, 0f);
GL.glVertex2f(shape.getPoints()[0] + distortionX, shape.getPoints()[1]);
//topright
GL.glTexCoord2f(1f, 0f);
GL.glVertex2f(shape.getPoints()[2] + distortionX, shape.getPoints()[3]);
//bottom right
GL.glTexCoord2f(1f, 1f);
GL.glVertex2f(shape.getPoints()[4], shape.getPoints()[5]);
//btoom left
GL.glTexCoord2f(0f, 1f);
GL.glVertex2f(shape.getPoints()[6], shape.getPoints()[7]);
GL.glEnd();
[...] if I feed an image into the method that was obtained using getSubImage, [...] the sprite itself is taken from a spritesheet [...]
The sprite is covers just a small rectangular region of the entire texture. This region is defined by the texture coordinates. You have to use the same texture coordinates as when you draw the sprite itself.

How to make smooth circle texture?

I am making libgdx game, and i want to have smooth circle character. Now i have 128 x 128 circle texture, which looks proppertly in paintnet but have ragged edges in game . I draw this texture by:
width=height=Gdx.graphics.getWidth()/4;
game.batch.draw(game.assets.good_guy,x,y,width,height);
I have tried to use photoshop, paintnet, gimp and inkscape but the texture was ragged all the time.
This is how it looks like in game:
And this is how looks texture:

try to keep the aspect ratio, if your texture is 128x128 and you as another ratio scales can show sawtooth, read about texture filtrer http://www.badlogicgames.com/wordpress/?p=1403 or use, svg or OpenVG Is there a way to incorporate vector graphics into LibGDX development?

OpenGL not drawing textured and non-textured quads simultaneously

I'm trying to draw a textured quad, then on top of that a black rectangle which has no texture. I use glEnable(GL_TEXTURE_2D) before I draw the textured quad and glDisable(GL_TEXTURE_2D) before I draw the non-textured quad, but My textured quad only appears for a split second and then I'm left with my clear color filling the entire screen and only the non-textured quad showing up. Why is this happening?
P.S: I call glClear(GL_COLOR_BUFFER_BIT) before doing any render work, not in between the render methods so that shouldn't be the problem I think
Also, I can only see the non-textured quad even if I draw the textured quad on top of it

I solved my problem. Turns out I didn't set a color before doing the textured quad so whenever i changed the color of the other quad this color is changing as well, so setting the color before binding the texture worked.

Java OpenGL only blue Textures

I've have a little Problem with Textures and OpenGL. I made a small .obj Loader (with Texture Loading) but everything is drawn blue. Example:
I load a Texture. I bind the texture with GL11.glBindTexture(GL11.GL_TEXTURE_2D,textureId).
If I do:
glColor3f(1f,1f,1f);
glBegin(GL_QUADS);
glVertex3f(50f,0,-50);
glVertex3f(-50f,0,-50f);
glVertex3f(-50f,0,50f);
glVertex3f(50f,0,50f);
glEnd();
GL11.glBindTexture(GL11.GL_TEXTURE_2D, textureId);
it draws a white quad ... but if I do:
GL11.glBindTexture(GL11.GL_TEXTURE_2D, textureId);
glColor3f(1f,1f,1f);
glBegin(GL_QUADS);
glVertex3f(50f,0,-50);
glVertex3f(-50f,0,-50f);
glVertex3f(-50f,0,50f);
glVertex3f(50f,0,50f);
glEnd();
it draws a blue quad and everything else is blue too.
Maybe somebody knows a solution?

There is no texture because you didn't specify texture coordinates using glTexCoord2f.
The colors are wrong probably due to incorrect parameters to glTexImage.
Everything else is blue because, you are using the same texture for everything. Bind different texture or use the default texture 0.

This is the problem because you are not using the glTexCoord2f with each vertex. Please try this with each vertex because it can solve it as presently your color is not binding to all the areas.

Ardor3D transparent quad

I am using Ardor3D for a 3D application in Java. I can draw a quad to the screen with a texture mapped to it. Part of the texture image is transparent, and the quad background shows through there.
How do you make the quad itself transparent, so the rendered scene will show through?

If your texture format supports an alpha channel (png, tga, dds, etc. but not jpg) then you just also need a BlendState. Something like:
BlendState blend = new BlendState();
blend.setBlendEnabled(true);
myQuad.setRenderState(blend);
You may also want to place your quad into the Transparent render queue if your quad is partially transparent (an alpha in between 0% and 100%) to get the correct sorting:
myQuad.getSceneHints().setRenderBucketType(RenderBucketType.Transparent);
There are other, non-alpha based ways to blend, but the above is usually what you want.