Android(安卓)OpenGL 文本显示 LabelMaker
16lz
2021-01-26
Android ApiDemos 里有个LabelMaker， 封装了OpenGl 的text lables的生产和显示，用起来非常方便：
LabelMaker： OpenGL text labels通过创建Bitmap、将所有text labels绘制到Bitmap、将Bitmap转换为alpha texture 以及使用gldrawtexios绘制部分texture来实现。
Example code:
import android.app.Activity;import android.graphics.Paint;import android.opengl.GLSurfaceView;import android.os.Bundle;import javax.microedition.khronos.egl.EGLConfig;import javax.microedition.khronos.opengles.GL10;public class TextLablesActivity extends Activity implements GLSurfaceView.Renderer{ private GLSurfaceView mGLView; private LabelMaker mLabels; private int mWidth; private int mHeight; private int mLabelId1; //text label id private int mLabelId2; //text label id @Override protected void onCreate( Bundle savedInstanceState) { super.onCreate(savedInstanceState); mGLView = new GLSurfaceView(this); mGLView.setRenderer(this); setContentView(mGLView); } @Override public void onDrawFrame(GL10 gl) { mLabels.beginDrawing(gl,mWidth,mHeight); mLabels.draw(gl,600,600, mLabelId1); //指定坐标，显示label 1 mLabels.draw(gl,600,700, mLabelId2); //指定坐标，显示label 2 mLabels.endDrawing(gl); } @Override public void onSurfaceCreated(GL10 gl, EGLConfig config) { //调用LabelMaker 生成text label mLabels = new LabelMaker(true, 1080, 256); //Bitmap的宽和高， 可以根据你的text lable来调整大小 Paint labelPaint = new Paint(); //text label的画笔 labelPaint.setTextSize(32); labelPaint.setAntiAlias(true); labelPaint.setARGB(0xff, 0xff, 0x00, 0x00); mLabels.initialize(gl); mLabels.beginAdding(gl); mLabelId1 = mLabels.add(gl,"OpenGL 显示的文字",labelPaint); //add lable1 mLabelId2 = mLabels.add(gl,"Hello world !",labelPaint); //add label2 mLabels.endAdding(gl); } @Override public void onSurfaceChanged(GL10 gl, int width, int height) { mWidth = width; mHeight = height; gl.glViewport(0, 0, width, height); float ratio = (float) width / height; gl.glMatrixMode(GL10.GL_PROJECTION); gl.glLoadIdentity(); gl.glFrustumf(-ratio, ratio, -1, 1, 1, 15); gl.glMatrixMode(GL10.GL_MODELVIEW); gl.glLoadIdentity(); }}
LabelMaker code：
import android.graphics.Bitmap;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.Rect;import android.graphics.Paint.Style;import android.graphics.drawable.Drawable;import android.opengl.GLUtils;import java.util.ArrayList;import javax.microedition.khronos.opengles.GL10;import javax.microedition.khronos.opengles.GL11;import javax.microedition.khronos.opengles.GL11Ext;/** * An OpenGL text label maker. * * * OpenGL labels are implemented by creating a Bitmap, drawing all the labels * into the Bitmap, converting the Bitmap into an Alpha texture, and drawing * portions of the texture using glDrawTexiOES. * * The benefits of this approach are that the labels are drawn using the high * quality anti-aliased font rasterizer, full character set support, and all the * text labels are stored on a single texture, which makes it faster to use. * * The drawbacks are that you can only have as many labels as will fit onto one * texture, and you have to recreate the whole texture if any label text * changes. * */public class LabelMaker { /** * Create a label maker * or maximum compatibility with various OpenGL ES implementations, * the strike width and height must be powers of two, * We want the strike width to be at least as wide as the widest window. * * @param fullColor true if we want a full color backing store (4444), * otherwise we generate a grey L8 backing store. * @param strikeWidth width of strike * @param strikeHeight height of strike */ public LabelMaker(boolean fullColor, int strikeWidth, int strikeHeight) { mFullColor = fullColor; mStrikeWidth = strikeWidth; mStrikeHeight = strikeHeight; mTexelWidth = (float) (1.0 / mStrikeWidth); mTexelHeight = (float) (1.0 / mStrikeHeight); mClearPaint = new Paint(); mClearPaint.setARGB(0, 0, 0, 0); mClearPaint.setStyle(Style.FILL); mState = STATE_NEW; } /** * Call to initialize the class. * Call whenever the surface has been created. * * @param gl */ public void initialize(GL10 gl) { mState = STATE_INITIALIZED; int[] textures = new int[1]; gl.glGenTextures(1, textures, 0); mTextureID = textures[0]; gl.glBindTexture(GL10.GL_TEXTURE_2D, mTextureID); // Use Nearest for performance. gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_NEAREST); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_NEAREST); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_CLAMP_TO_EDGE); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_CLAMP_TO_EDGE); gl.glTexEnvf(GL10.GL_TEXTURE_ENV, GL10.GL_TEXTURE_ENV_MODE, GL10.GL_REPLACE); } /** * Call when the surface has been destroyed */ public void shutdown(GL10 gl) { if ( gl != null) { if (mState > STATE_NEW) { int[] textures = new int[1]; textures[0] = mTextureID; gl.glDeleteTextures(1, textures, 0); mState = STATE_NEW; } } } /** * Call before adding labels. Clears out any existing labels. * * @param gl */ public void beginAdding(GL10 gl) { checkState(STATE_INITIALIZED, STATE_ADDING); mLabels.clear(); mU = 0; mV = 0; mLineHeight = 0; Bitmap.Config config = mFullColor ? Bitmap.Config.ARGB_4444 : Bitmap.Config.ALPHA_8; mBitmap = Bitmap.createBitmap(mStrikeWidth, mStrikeHeight, config); mCanvas = new Canvas(mBitmap); mBitmap.eraseColor(0); } /** * Call to add a label * * @param gl * @param text the text of the label * @param textPaint the paint of the label * @return the id of the label, used to measure and draw the label */ public int add(GL10 gl, String text, Paint textPaint) { return add(gl, null, text, textPaint); } /** * Call to add a label * * @param gl * @param text the text of the label * @param textPaint the paint of the label * @return the id of the label, used to measure and draw the label */ public int add(GL10 gl, Drawable background, String text, Paint textPaint) { return add(gl, background, text, textPaint, 0, 0); } /** * Call to add a label * @return the id of the label, used to measure and draw the label */ public int add(GL10 gl, Drawable drawable, int minWidth, int minHeight) { return add(gl, drawable, null, null, minWidth, minHeight); } /** * Call to add a label * * @param gl * @param text the text of the label * @param textPaint the paint of the label * @return the id of the label, used to measure and draw the label */ public int add(GL10 gl, Drawable background, String text, Paint textPaint, int minWidth, int minHeight) { checkState(STATE_ADDING, STATE_ADDING); boolean drawBackground = background != null; boolean drawText = (text != null) && (textPaint != null); Rect padding = new Rect(); if (drawBackground) { background.getPadding(padding); minWidth = Math.max(minWidth, background.getMinimumWidth()); minHeight = Math.max(minHeight, background.getMinimumHeight()); } int ascent = 0; int descent = 0; int measuredTextWidth = 0; if (drawText) { // Paint.ascent is negative, so negate it. ascent = (int) Math.ceil(-textPaint.ascent()); descent = (int) Math.ceil(textPaint.descent()); measuredTextWidth = (int) Math.ceil(textPaint.measureText(text)); } int textHeight = ascent + descent; int textWidth = Math.min(mStrikeWidth,measuredTextWidth); int padHeight = padding.top + padding.bottom; int padWidth = padding.left + padding.right; int height = Math.max(minHeight, textHeight + padHeight); int width = Math.max(minWidth, textWidth + padWidth); int effectiveTextHeight = height - padHeight; int effectiveTextWidth = width - padWidth; int centerOffsetHeight = (effectiveTextHeight - textHeight) / 2; int centerOffsetWidth = (effectiveTextWidth - textWidth) / 2; // Make changes to the local variables, only commit them // to the member variables after we've decided not to throw // any exceptions. int u = mU; int v = mV; int lineHeight = mLineHeight; if (width > mStrikeWidth) { width = mStrikeWidth; } // Is there room for this string on the current line? if (u + width > mStrikeWidth) { // No room, go to the next line: u = 0; v += lineHeight; lineHeight = 0; } lineHeight = Math.max(lineHeight, height); if (v + lineHeight > mStrikeHeight) { throw new IllegalArgumentException("Out of texture space."); } int u2 = u + width; int vBase = v + ascent; int v2 = v + height; if (drawBackground) { background.setBounds(u, v, u + width, v + height); background.draw(mCanvas); } if (drawText) { mCanvas.drawText(text, u + padding.left + centerOffsetWidth, vBase + padding.top + centerOffsetHeight, textPaint); } // We know there's enough space, so update the member variables mU = u + width; mV = v; mLineHeight = lineHeight; mLabels.add(new Label(width, height, ascent, u, v + height, width, -height)); return mLabels.size() - 1; } /** * Call to end adding labels. Must be called before drawing starts. * * @param gl */ public void endAdding(GL10 gl) { checkState(STATE_ADDING, STATE_INITIALIZED); gl.glBindTexture(GL10.GL_TEXTURE_2D, mTextureID); GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, mBitmap, 0); // Reclaim storage used by bitmap and canvas. mBitmap.recycle(); mBitmap = null; mCanvas = null; } /** * Get the width in pixels of a given label. * * @param labelID * @return the width in pixels */ public float getWidth(int labelID) { return mLabels.get(labelID).width; } /** * Get the height in pixels of a given label. * * @param labelID * @return the height in pixels */ public float getHeight(int labelID) { return mLabels.get(labelID).height; } /** * Get the baseline of a given label. That's how many pixels from the top of * the label to the text baseline. (This is equivalent to the negative of * the label's paint's ascent.) * * @param labelID * @return the baseline in pixels. */ public float getBaseline(int labelID) { return mLabels.get(labelID).baseline; } /** * Begin drawing labels. Sets the OpenGL state for rapid drawing. * * @param gl * @param viewWidth * @param viewHeight */ public void beginDrawing(GL10 gl, float viewWidth, float viewHeight) { checkState(STATE_INITIALIZED, STATE_DRAWING); gl.glBindTexture(GL10.GL_TEXTURE_2D, mTextureID); gl.glShadeModel(GL10.GL_FLAT); gl.glEnable(GL10.GL_BLEND); gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA); gl.glColor4x(0x10000, 0x10000, 0x10000, 0x10000); gl.glMatrixMode(GL10.GL_PROJECTION); gl.glPushMatrix(); gl.glLoadIdentity(); gl.glOrthof(0.0f, viewWidth, 0.0f, viewHeight, 0.0f, 1.0f); gl.glMatrixMode(GL10.GL_MODELVIEW); gl.glPushMatrix(); gl.glLoadIdentity(); // Magic offsets to promote consistent rasterization. gl.glTranslatef(0.375f, 0.375f, 0.0f); } /** * Draw a given label at a given x,y position, expressed in pixels, with the * lower-left-hand-corner of the view being (0,0). * * @param gl * @param x * @param y * @param labelID */ public void draw(GL10 gl, float x, float y, int labelID) { checkState(STATE_DRAWING, STATE_DRAWING); Label label = mLabels.get(labelID); gl.glEnable(GL10.GL_TEXTURE_2D); ((GL11)gl).glTexParameteriv(GL10.GL_TEXTURE_2D, GL11Ext.GL_TEXTURE_CROP_RECT_OES, label.mCrop, 0); ((GL11Ext)gl).glDrawTexiOES((int) x, (int) y, 0, (int) label.width, (int) label.height); } /** * Ends the drawing and restores the OpenGL state. * * @param gl */ public void endDrawing(GL10 gl) { checkState(STATE_DRAWING, STATE_INITIALIZED); gl.glDisable(GL10.GL_BLEND); gl.glMatrixMode(GL10.GL_PROJECTION); gl.glPopMatrix(); gl.glMatrixMode(GL10.GL_MODELVIEW); gl.glPopMatrix(); } private void checkState(int oldState, int newState) { if (mState != oldState) { throw new IllegalArgumentException("Can't call this method now."); } mState = newState; } private static class Label { public Label(float width, float height, float baseLine, int cropU, int cropV, int cropW, int cropH) { this.width = width; this.height = height; this.baseline = baseLine; int[] crop = new int[4]; crop[0] = cropU; crop[1] = cropV; crop[2] = cropW; crop[3] = cropH; mCrop = crop; } public float width; public float height; public float baseline; public int[] mCrop; } private int mStrikeWidth; private int mStrikeHeight; private boolean mFullColor; private Bitmap mBitmap; private Canvas mCanvas; private Paint mClearPaint; private int mTextureID; private float mTexelWidth; // Convert texel to U private float mTexelHeight; // Convert texel to V private int mU; private int mV; private int mLineHeight; private ArrayList
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