java – IText阅读PDF格式如pdftotext -layout？
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我正在寻找一种最简单的方法来实现一个类似于输出的安静的java解决方案
pdftotext -layout FILE
在linux机器上. (当然它也应该便宜)
我刚刚尝试了一些IText,PDFBox和PDFTextStream的代码片段.到目前为止,最准确的解决方案是PDFTextStream,它使用VisualOutputTarget来获得我文件的绝佳表示.
所以我的列布局被认为是正确的,我能够使用它.
但是IText也应该有一个解决方案,或者？
我发现的每个简单片段都会生成简单有序的字符串,这些字符串很混乱(乱七八糟的行/列/行).是否有任何解决方案可能更容易,可能不涉及自己的战略？或者是否有可以使用的开源策略？
//我按照mkl的说明编写了自己的策略对象,如下所示：
package com.test.pdfextractiontest.itext;
import ...
public class MyLocationTextExtractionStrategy implements TextExtractionStrategy {
/** set to true for debugging */
static boolean DUMP_STATE = false;
/** a summary of all found text */
private final List<TextChunk> locationalResult = new ArrayList<TextChunk>();
public MyLocationTextExtractionStrategy() {
}
@Override
public void beginTextBlock() {
}
@Override
public void endTextBlock() {
}
private boolean startsWithSpace(final String str) {
if (str.length() == 0) {
return false;
}
return str.charAt(0) == ' ';
}
private boolean endsWithSpace(final String str) {
if (str.length() == 0) {
return false;
}
return str.charAt(str.length() - 1) == ' ';
}
private List<TextChunk> filterTextChunks(final List<TextChunk> textChunks, final TextChunkFilter filter) {
if (filter == null) {
return textChunks;
}
final List<TextChunk> filtered = new ArrayList<TextChunk>();
for (final TextChunk textChunk : textChunks) {
if (filter.accept(textChunk)) {
filtered.add(textChunk);
}
}
return filtered;
}
protected boolean isChunkAtWordBoundary(final TextChunk chunk, final TextChunk previousChunk) {
final float dist = chunk.distanceFromEndOf(previousChunk);
if (dist < -chunk.getCharSpaceWidth() || dist > chunk.getCharSpaceWidth() / 2.0f) {
return true;
}
return false;
}
public String getResultantText(final TextChunkFilter chunkFilter) {
if (DUMP_STATE) {
dumpState();
}
final List<TextChunk> filteredTextChunks = filterTextChunks(this.locationalResult, chunkFilter);
Collections.sort(filteredTextChunks);
final StringBuffer sb = new StringBuffer();
TextChunk lastChunk = null;
for (final TextChunk chunk : filteredTextChunks) {
if (lastChunk == null) {
sb.append(chunk.text);
} else {
if (chunk.sameLine(lastChunk)) {
if (isChunkAtWordBoundary(chunk, lastChunk) && !startsWithSpace(chunk.text)
&& !endsWithSpace(lastChunk.text)) {
sb.append(' ');
}
final Float dist = chunk.distanceFromEndOf(lastChunk)/3;
for(int i = 0; i<Math.round(dist); i++) {
sb.append(' ');
}
sb.append(chunk.text);
} else {
sb.append('\n');
sb.append(chunk.text);
}
}
lastChunk = chunk;
}
return sb.toString();
}
使用生成的文本生成一个String.
* /
@覆盖
public String getResultantText(){
return getResultantText(null);
}
private void dumpState() {
for (final TextChunk location : this.locationalResult) {
location.printDiagnostics();
System.out.println();
}
}
@Override
public void renderText(final TextRenderInfo renderInfo) {
LineSegment segment = renderInfo.getBaseline();
if (renderInfo.getRise() != 0) {
final Matrix riseOffsetTransform = new Matrix(0, -renderInfo.getRise());
segment = segment.transformBy(riseOffsetTransform);
}
final TextChunk location =
new TextChunk(renderInfo.getText(), segment.getStartPoint(), segment.getEndPoint(),
renderInfo.getSingleSpaceWidth(),renderInfo);
this.locationalResult.add(location);
}
public static class TextChunk implements Comparable<TextChunk> {
/** the text of the chunk */
private final String text;
/** the starting location of the chunk */
private final Vector startLocation;
/** the ending location of the chunk */
private final Vector endLocation;
/** unit vector in the orientation of the chunk */
private final Vector orientationVector;
/** the orientation as a scalar for quick sorting */
private final int orientationMagnitude;
private final TextRenderInfo info;
private final int distPerpendicular;
private final float distParallelStart;
private final float distParallelEnd;
/** the width of a single space character in the font of the chunk */
private final float charSpaceWidth;
public TextChunk(final String string, final Vector startLocation, final Vector endLocation,
final float charSpaceWidth,final TextRenderInfo ri) {
this.text = string;
this.startLocation = startLocation;
this.endLocation = endLocation;
this.charSpaceWidth = charSpaceWidth;
this.info = ri;
Vector oVector = endLocation.subtract(startLocation);
if (oVector.length() == 0) {
oVector = new Vector(1, 0, 0);
}
this.orientationVector = oVector.normalize();
this.orientationMagnitude =
(int) (Math.atan2(this.orientationVector.get(Vector.I2), this.orientationVector.get(Vector.I1)) * 1000);
final Vector origin = new Vector(0, 0, 1);
this.distPerpendicular = (int) startLocation.subtract(origin).cross(this.orientationVector).get(Vector.I3);
this.distParallelStart = this.orientationVector.dot(startLocation);
this.distParallelEnd = this.orientationVector.dot(endLocation);
}
public Vector getStartLocation() {
return this.startLocation;
}
public Vector getEndLocation() {
return this.endLocation;
}
public String getText() {
return this.text;
}
public float getCharSpaceWidth() {
return this.charSpaceWidth;
}
private void printDiagnostics() {
System.out.println("Text (@" + this.startLocation + " -> " + this.endLocation + "): " + this.text);
System.out.println("orientationMagnitude: " + this.orientationMagnitude);
System.out.println("distPerpendicular: " + this.distPerpendicular);
System.out.println("distParallel: " + this.distParallelStart);
}
public boolean sameLine(final TextChunk as) {
if (this.orientationMagnitude != as.orientationMagnitude) {
return false;
}
if (this.distPerpendicular != as.distPerpendicular) {
return false;
}
return true;
}
public float distanceFromEndOf(final TextChunk other) {
final float distance = this.distParallelStart - other.distParallelEnd;
return distance;
}
public float myDistanceFromEndOf(final TextChunk other) {
final float distance = this.distParallelStart - other.distParallelEnd;
return distance;
}
@Override
public int compareTo(final TextChunk rhs) {
if (this == rhs) {
return 0; // not really needed, but just in case
}
int rslt;
rslt = compareInts(this.orientationMagnitude, rhs.orientationMagnitude);
if (rslt != 0) {
return rslt;
}
rslt = compareInts(this.distPerpendicular, rhs.distPerpendicular);
if (rslt != 0) {
return rslt;
}
return Float.compare(this.distParallelStart, rhs.distParallelStart);
}
private static int compareInts(final int int1, final int int2) {
return int1 == int2 ? 0 : int1 < int2 ? -1 : 1;
}
public TextRenderInfo getInfo() {
return this.info;
}
}
@Override
public void renderImage(final ImageRenderInfo renderInfo) {
// do nothing
}
public static interface TextChunkFilter {
public boolean accept(TextChunk textChunk);
}
}
正如您所看到的,大多数与原始类相同.我刚添加了这个：
final Float dist = chunk.distanceFromEndOf(lastChunk)/3;
for(int i = 0; i<Math.round(dist); i++) {
sb.append(' ');
}
到getResultantText方法用空格扩展间隙.
但问题出在这里：
距离似乎不准确或不准确.结果看起来像
这个：
有没有人知道如何计算更好的距离或价值？我认为它是因为原始字体类型是ArialMT而我的编辑器是快递的,但是为了使用这张表,我建议我可以将表拆分到正确的位置以获取我的数据.由于浮动开始和结束值usw,这很难.
： – /
解决方法:
你的方法插入这样的空间的问题
final Float dist = chunk.distanceFromEndOf(lastChunk)/3;
for(int i = 0; i<Math.round(dist); i++) {
sb.append(' ');
}
假设字符宽度宽度为3个用户空间单位,它假定StringBuffer中的当前位置与lastChunk的末尾完全对应.不一定是这种情况,通常每次添加字符都会破坏这种以前的对应关系.例如.使用比例字体时,这两行的宽度不同：
ililili
MWMWMWM
而在StringBuffer中,它们占用相同的长度.
因此,您必须查看块相对于左页边框的起始位置,并相应地向缓冲区添加空格.
此外,您的代码完全忽略了行首的自由空间.
如果您使用此代码替换原始方法getResultantText(TextChunkFilter),您的结果应该会改进：
public String getResultantText(TextChunkFilter chunkFilter){
if (DUMP_STATE) dumpState();
List<TextChunk> filteredTextChunks = filterTextChunks(locationalResult, chunkFilter);
Collections.sort(filteredTextChunks);
int startOfLinePosition = 0;
StringBuffer sb = new StringBuffer();
TextChunk lastChunk = null;
for (TextChunk chunk : filteredTextChunks) {
if (lastChunk == null){
insertSpaces(sb, startOfLinePosition, chunk.distParallelStart, false);
sb.append(chunk.text);
} else {
if (chunk.sameLine(lastChunk))
{
if (isChunkAtWordBoundary(chunk, lastChunk))
{
insertSpaces(sb, startOfLinePosition, chunk.distParallelStart, !startsWithSpace(chunk.text) && !endsWithSpace(lastChunk.text));
}
sb.append(chunk.text);
} else {
sb.append('\n');
startOfLinePosition = sb.length();
insertSpaces(sb, startOfLinePosition, chunk.distParallelStart, false);
sb.append(chunk.text);
}
}
lastChunk = chunk;
}
return sb.toString();
}
void insertSpaces(StringBuffer sb, int startOfLinePosition, float chunkStart, boolean spaceRequired)
{
int indexNow = sb.length() - startOfLinePosition;
int indexToBe = (int)((chunkStart - pageLeft) / fixedCharWidth);
int spacesToInsert = indexToBe - indexNow;
if (spacesToInsert < 1 && spaceRequired)
spacesToInsert = 1;
for (; spacesToInsert > 0; spacesToInsert--)
{
sb.append(' ');
}
}
public float pageLeft = 0;
public float fixedCharWidth = 6;
pageLeft是左页边框的坐标.该战略不了解它,因此必须明确告知;但在许多情况下,0是正确的值.
或者,可以使用所有块的最小distParallelStart值.这会切断左边距,但不会要求您注入精确的左页边框值.
fixedCharWidth是假定的字符宽度.根据相关PDF中的书写,不同的值可能更适合.在你的情况下,值3似乎比我的6更好.
此代码仍有很大的改进空间.例如.
>它假定没有跨多个表列的文本块.这种假设通常是正确的,但我已经看到了奇怪的PDF,其中在一些偏移处使用单独的文本块实现了正常的字间距,但是列间间距由单个块中的单个空格字符表示(跨越)一列的结尾和下一列的开头)！该空格字符的宽度已由PDF图形状态的字间距设置操纵.
>它忽略了不同数量的垂直空间.
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