我正在尝试在反应原生的 GLView 上显示图像。我受到此链接的启发来编写我的代码https://webglfundamentals.org/webgl/lessons/webgl-2d-drawimage.html
我有这个调用 GLContext2D 类的组件：
import React, { Component } from 'react';
import { Text, View, StyleSheet } from 'react-native';
import Expo from 'expo';
import GLContext2D from '../../lib/GLContext2D';
export default class Scene extends Component {
constructor(props, context) {
super(props, context);
this.state = {
ready: false,
};
}
componentDidMount() {
(async () => {
this._textureAsset = Expo.Asset.fromModule(
require('../../test.jpg')
);
await this._textureAsset.downloadAsync();
console.log("ok");
this.setState({ ready: true });
})();
}
render () {
return this.state.ready
? <Expo.GLView
style={styles.view}
onContextCreate={this._onContextCreate}
/>
: <Expo.AppLoading />;
}
_onContextCreate = gl => {
console.log(this._textureAsset);
var ctx = new GLContext2D(gl);
var test = ctx.createTextureFromAsset(this._textureAsset);
ctx.clear();
gl.clearColor(0, 0, 1, 1);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
ctx.drawImage(test.texture, test.width, test.height, 0, 200);
gl.flush();
gl.endFrameEXP();
}
}
const styles = StyleSheet.create({
view: {
width: 500,
height: 1000,
backgroundColor: 'yellow'
}
});和 GLContext2D 类：
import Expo from 'expo';
import {mat4} from 'gl-matrix';
const vertSrc = `
attribute vec4 a_position;
attribute vec2 a_texcoord;
uniform mat4 u_matrix;
uniform mat4 u_textureMatrix;
varying vec2 v_texcoord;
void main() {
gl_Position = u_matrix * a_position;
v_texcoord = (u_textureMatrix * vec4(a_texcoord, 0, 1)).xy;
}
`;
const fragSrc = `
precision mediump float;
varying vec2 v_texcoord;
uniform sampler2D u_texture;
void main() {
if (v_texcoord.x < 0.0 ||
v_texcoord.y < 0.0 ||
v_texcoord.x > 1.0 ||
v_texcoord.y > 1.0) {
gl_FragColor = vec4(1, 0, 1, 1); // blue
return;
}
gl_FragColor = texture2D(u_texture, v_texcoord);
}
`;
export default class GLContext2D {
constructor(gl) {
var vert;
var frag;
this._gl = gl;
vert = gl.createShader(gl.VERTEX_SHADER);
gl.shaderSource(vert, vertSrc);
gl.compileShader(vert);
frag = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(frag, fragSrc);
gl.compileShader(frag);
this._program = gl.createProgram();
gl.attachShader(this._program, vert);
gl.attachShader(this._program, frag);
gl.linkProgram(this._program);
this._locations = {
position: gl.getAttribLocation(this._program, "a_position"),
texcoord: gl.getAttribLocation(this._program, "a_texcoord"),
matrix: gl.getUniformLocation(this._program, "u_matrix"),
textureMatrix: gl.getUniformLocation(this._program, "u_textureMatrix"),
texture: gl.getUniformLocation(this._program, "u_texture")
};
this._createBuffers();
}
_createBuffers() {
var positions;
var texcoords;
var gl;
gl = this._gl;
this._positionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, this._positionBuffer);
positions = [0, 0, 0, 1, 1, 0, 1, 0, 0, 1, 1, 1];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);
this._texcoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, this._texcoordBuffer);
texcoords = [0, 0, 0, 1, 1, 0, 1, 0, 0, 1, 1, 1];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(texcoords), gl.STATIC_DRAW);
}
async createTextureFromAsset(asset) {
var gl;
var tex;
var texData;
var img;
gl = this._gl;
tex = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE,
new Uint8Array([0, 0, 255, 255]));
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
texData = {
width: 1,
height: 1,
texture: tex,
};
texData.width = asset.width;
texData.height = asset.height;
gl.bindTexture(gl.TEXTURE_2D, texData.texture);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, asset);
return (texData);
}
//ctx.drawImage(tex, texWidth, texHeight, dstX, dstY);
//ctx.drawImage(tex, texWidth, texHeight, dstX, dstY, dstWidth, dstHeight)
drawImage(
tex, texWidth, texHeight,
srcX, srcY, srcWidth, srcHeight,
dstX, dstY, dstWidth, dstHeight, srcRotation) {
var gl;
var matrix, matrix2;
var texMatrix;
if (dstX === undefined) {
dstX = srcX;
srcX = 0;
}
if (dstY === undefined) {
dstY = srcY;
srcY = 0;
}
if (srcWidth === undefined) {
srcWidth = texWidth;
}
if (srcHeight === undefined) {
srcHeight = texHeight;
}
if (dstWidth === undefined) {
dstWidth = srcWidth;
srcWidth = texWidth;
}
if (dstHeight === undefined) {
dstHeight = srcHeight;
srcHeight = texHeight;
}
if (srcRotation === undefined) {
srcRotation = 0;
}
gl = this._gl;
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.useProgram(this._program);
gl.bindBuffer(gl.ARRAY_BUFFER, this._positionBuffer);
gl.enableVertexAttribArray(this._locations.position);
gl.vertexAttribPointer(this._locations.position, 2, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ARRAY_BUFFER, this._texcoordBuffer);
gl.enableVertexAttribArray(this._locations.texcoord);
gl.vertexAttribPointer(this._locations.texcoord, 2, gl.FLOAT, false, 0, 0);
matrix = mat4.create();
matrix2 = mat4.create();
mat4.ortho(matrix, 0, 1000, 1000, 0, -1, 1);
mat4.translate(matrix2, matrix, [dstX, dstY, 0]);
mat4.copy(matrix, matrix2);
mat4.scale(matrix2, matrix, [dstWidth, dstHeight, 1]);
mat4.copy(matrix, matrix2);
gl.drawingBufferHeight = 320;
gl.uniformMatrix4fv(this._locations.matrix, false, matrix);
texMatrix = mat4.create();
mat4.fromScaling(texMatrix, [1 / texWidth, 1 / texHeight, 1]);
mat4.translate(matrix2, texMatrix, [texWidth * 0.5, texHeight * 0.5, 0]);
mat4.copy(texMatrix, matrix2);
mat4.rotateZ(matrix2, texMatrix, srcRotation);
mat4.copy(texMatrix, matrix2);
mat4.translate(matrix2, texMatrix, [texWidth * -0.5, texHeight * -0.5, 0]);
mat4.translate(texMatrix, matrix2, [srcX, srcY, 0]);
mat4.scale(matrix2, texMatrix, [srcWidth, srcHeight, 1]);
mat4.copy(texMatrix, matrix2);
gl.uniformMatrix4fv(this._locations.textureMatrix, false, texMatrix);
gl.uniform1i(this._locations.texture, 0);
gl.drawArrays(gl.TRIANGLES, 0, 6);
}
clear() {
var gl;
gl = this._gl;
gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight);
gl.clear(gl.COLOR_BUFFER_BIT);
}
}
我有一个带有 clear 功能的蓝屏，但 drawImage 函数没有显示任何内容。