add icdar2015 download

doc/doc_ch/detection.md

@@ -25,7 +25,7 @@ icdar2015数据集可以从[官网](https://rrc.cvc.uab.es/?ch=4&com=downloads)
 注册完成登陆后，下载下图中红色框标出的部分，其中， `Training Set Images`下载的内容保存为`icdar_c4_train_imgs`文件夹下，`Test Set Images` 下载的内容保存为`ch4_test_images`文件夹下
 
 <p align="center">
- <img src="../datasets/ic15_location_download.png" align="middle" width = "600"/>
+ <img src="../datasets/ic15_location_download.png" align="middle" width = "700"/>
 <p align="center">
 
 将下载到的数据集解压到工作目录下，假设解压在 PaddleOCR/train_data/下。另外，PaddleOCR将零散的标注文件整理成单独的标注文件

doc/doc_en/detection_en.md

@@ -25,7 +25,7 @@ The icdar2015 dataset contains train set which has 1000 images obtained with wea
 After registering and logging in, download the part marked in the red box in the figure below. And, the content downloaded by `Training Set Images` should be saved as the folder `icdar_c4_train_imgs`, and the content downloaded by `Test Set Images` is saved as the folder `ch4_test_images`
 
 <p align="center">
- <img src="../datasets/ic15_location_download.png" align="middle" width = "600"/>
+ <img src="../datasets/ic15_location_download.png" align="middle" width = "700"/>
 <p align="center">
 
 Decompress the downloaded dataset to the working directory, assuming it is decompressed under PaddleOCR/train_data/. In addition, PaddleOCR organizes many scattered annotation files into two separate annotation files for train and test respectively, which can be downloaded by wget: