image-processing - Mathematica 的 TextRecognize 达不到标准

Question

请查看下面的屏幕截图，看看您能否告诉我为什么这不起作用。TextRecognize 参考页面上的示例看起来非常令人印象深刻，我认为识别这样的单个字母应该不是问题。我试过调整字母的大小以及锐化图像。

为了方便您自己尝试一下，我在这篇文章的底部包含了我使用的图像。您还可以通过在 Google 图片搜索中搜索“Wordfeud”来找到更多类似的内容。

Answer 1

Very cool question!

TextRecognize uses heuristics to recognize whole words from the English language. This is the gotcha that makes recognizing single letters very hard

Consider the following line of thought:

s = Import["http://i.stack.imgur.com/JHYuh.png"];
p = ImagePartition[s, 32]

Now pick letters to form the English word 'EXIT':

x = {p[[1, 13]], p[[6, 6]], p[[3, 13]], p[[1, 12]]}

Now clean up these images a bit, like so:

d = ImageAssemble[ Map[ImageTake[#, {3, 27}, {2, 20}] &, x ]];

Then this returns the string "EXIT":

TextRecognize[d]

Answer 2

这是一种与使用 TextRecognize 完全不同的方法，因此我将其作为单独的答案发布。它使用How do I find Waldo with Mathematica中的相同图像识别技术。

首先得到谜题：

wordfeud = Import["http://i.stack.imgur.com/JHYuh.png"]

然后得到拼图的碎片：

Grid[pieces = ImagePartition[s, 32]]

让我们对字母 E 感兴趣：

LetterE = pieces[[4, 3]]

获取相关图像：

correlation = 
 ImageCorrelate[wordfeud, Binarize[LetterE], 
 NormalizedSquaredEuclideanDistance]

并突出显示比赛：

positions = Dilation[ColorNegate[Binarize[correlation, .1]], DiskMatrix[20]];
found = ImageMultiply[wordfeud, ImageAdd[ColorConvert[positions, "GrayLevel"], .5]]

和以前一样，这需要对相关图像的二值化进行一些调整，但除此之外，这应该有助于识别这个难题的点点滴滴。

Answer 3

I thought the quality of your image might be interfering. Binarizing your image did not help : recognition was zilch. I also tried a very sharp black and white image of a crossword puzzle solution. (see below) Again, nothing was recognized whether in regular or binarized format.

So I removed the black background leaving only the letters and their thin black frames. Again, recognition was about 0%.

When I removed the frames from around some of the letters AND binarized the image the only parts that were recognizable were those regions in which there was nothing but letters. (see below)

Notice in the output below, ANTS, TIRES, and TEXAS are correctly identified (as well as VECTORS), but just about nothing else.

Notice also that, even though the strings were widely spaced, mma interpreted them as words, rather than separate letters. Note "TEXAS" instead of "T E X A S".

TextRecognize[Binarize@img]

(* output *)
ANTS FFWWW FEEWF
E R o If IU I?
E A FI5F WWWFF 5
5552? L E F F
T s E NTT BT|
H0RWW@0WVlWF;EE F
5 W E   ; OCS
FOFT W W R AL%AE
A TT I T ? _
i iE@W'NF WG%S W
A A EW F I i
SWWTW W ALTFCWD N
H A V 5 A F F
PLATT EWWLIGHT
W N E T
HE TIRES C
TEXAS VECTORS

I didn't have the patience to completely clean up the image. It would have been much faster to retype the text by hand.

Conclusion: Don't use text recognition in mma unless you have absolutely clear text against an even-colored, bright, preferrably white, background.

The results also varied depending on the file format used. Avoid .pdf altogether.

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Edit

acl captured and tried to recognize the last 5 lines (above Edit). His results (in a comment below): mostly gibberish.

I decided to do the same. But since Prashant warned that text size makes a difference, I zoomed in first so that the text appear (to my eyes) to be about 20 pica. Below is the picture of the text I scanned and TextRecognized.

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Here's the result of an unbinarized TextRecognize (at that large size):

Gliii. Q lk-ii`t`*¥ if EY £\[CloseCurlyDoubleQuote]1\[Euro]'EE \
Di'¥C~E\"P ITF SKI' T»f}!E'!',IL:?E\[CloseCurlyDoubleQuote] I 2 VEEE5\
\[CloseCurlyQuote] LEP \"- \"VE
1. ur e=\\..r.1.»».»\\\\ rw r 1»»\\|a'*r | r .fm -»'-an \
\[OpenCurlyQuote] -.-rr -_.»~|-.'i~-.w~,.-- nv n.w~»-\
\[OpenCurlyDoubleQuote]~"

Now, here's the result for the TextRecognize of the binarized image. The original image was a .png from Jing.

I didn't have the patience to completely clean up the image. It would \
have been much faster to retype the
text by hand.
Conclusion: Don't use text recognition in mma unless you have \
absolutely clear text against an even-
colored, bright, preferrably white, background.
The results also varied depending on the file format used. Avoid .pdf \
altogether.