Distort image with shader

@yangyangcv wrote:

say i have an image like below:

1.jpg1024x657 264 KB

this is the effect i want to achieve:

3.jpg1024x657 295 KB

but acturally i get this:

4.jpg1026x740 197 KB

below are the codes:

ofApp.h

#pragma once

#include "ofMain.h"

class ofApp : public ofBaseApp{
	public:
		
	void setup();
	void update();
	void draw();
	
	void keyPressed(int key);
	void keyReleased(int key);
	void mouseMoved(int x, int y);
	void mouseDragged(int x, int y, int button);
	void mousePressed(int x, int y, int button);
	void mouseReleased(int x, int y, int button);
	void windowResized(int w, int h);
	void dragEvent(ofDragInfo dragInfo);
	void gotMessage(ofMessage msg);

    ofShader shader;

	ofImage img;
};

ofApp.cpp

#include "ofApp.h"

//--------------------------------------------------------------
void ofApp::setup(){
    
	ofBackground(0);
	shader.load("shadersGL3/shader");
	if(!img.loadImage("1.jpg"))
		std::cout<<"fail to load 1.jpg"<<std::endl;
}

//--------------------------------------------------------------
void ofApp::update(){

}

//--------------------------------------------------------------
void ofApp::draw(){

    shader.begin();
	img.draw(0,0);
    shader.end();
}

shader.frag

#version 150

uniform sampler2DRect tex0;

in vec2 texCoordVarying;
out vec4 outputColor;

void main()
{
    vec4 color;
    color = texture(tex0, texCoordVarying );
    outputColor = color;
}

shader.vert

#version 150

uniform mat4 modelViewProjectionMatrix;
in vec4 position;
in vec2 texcoord;
out vec2 texCoordVarying;
void main()
{
	texCoordVarying = texcoord;
    vec4 modifiedPosition = modelViewProjectionMatrix * position;
	gl_Position = modifiedPosition;
	if(gl_Position.x<500){
		gl_Position.y -= 140;
	}
}

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