我想实现，承认从图片文字的OCR应用程序。
我成功地在iOS的编译和整合的正方体引擎，我成功地得到拍摄清晰的文档时，合理的检测（或从屏幕这段文字的拍照），但对于其他的文本，如路标，商店招牌，彩色背景，检测不合格。
现在的问题是一种图像处理的准备是必要的，以获得更好的识别什么。 例如，我期望我们需要将图像变换为灰度/ B＆W以及定影对比度等
这又如何在iOS中进行，是否有一个包呢？
Answer 1:
我目前正在对同样的事情。 我发现，保存在Photoshop PNG工作得很好，但它最初是从摄像机然后导入到应用程序源的图像从来没有工作过。 不要问我解释了吧 - 但使用该功能使这些图像的工作。 也许它会为你工作了。
// this does the trick to have tesseract accept the UIImage.
UIImage * gs_convert_image (UIImage * src_img) {
CGColorSpaceRef d_colorSpace = CGColorSpaceCreateDeviceRGB();
/*
* Note we specify 4 bytes per pixel here even though we ignore the
* alpha value; you can't specify 3 bytes per-pixel.
*/
size_t d_bytesPerRow = src_img.size.width * 4;
unsigned char * imgData = (unsigned char*)malloc(src_img.size.height*d_bytesPerRow);
CGContextRef context = CGBitmapContextCreate(imgData, src_img.size.width,
src_img.size.height,
8, d_bytesPerRow,
d_colorSpace,
kCGImageAlphaNoneSkipFirst);
UIGraphicsPushContext(context);
// These next two lines 'flip' the drawing so it doesn't appear upside-down.
CGContextTranslateCTM(context, 0.0, src_img.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
// Use UIImage's drawInRect: instead of the CGContextDrawImage function, otherwise you'll have issues when the source image is in portrait orientation.
[src_img drawInRect:CGRectMake(0.0, 0.0, src_img.size.width, src_img.size.height)];
UIGraphicsPopContext();
/*
* At this point, we have the raw ARGB pixel data in the imgData buffer, so
* we can perform whatever image processing here.
*/
// After we've processed the raw data, turn it back into a UIImage instance.
CGImageRef new_img = CGBitmapContextCreateImage(context);
UIImage * convertedImage = [[UIImage alloc] initWithCGImage:
new_img];
CGImageRelease(new_img);
CGContextRelease(context);
CGColorSpaceRelease(d_colorSpace);
free(imgData);
return convertedImage;
}
我也走了很多的试验准备图像正方体。 调整大小，转换为灰度，然后调整亮度和对比度似乎工作最好的。
我也试过这个GPUImage库。 https://github.com/BradLarson/GPUImage而GPUImageAverageLuminanceThresholdFilter似乎给了我很大的调整后的图像，但正方体似乎并不与它很好地工作。
我也把OpenCV的到我的项目，并计划尝试它的形象例程。 甚至可能有些盒检测发现文本区域（我希望这将加快正方体）。
Answer 2:
我用上面的代码，加入其他两个函数调用，以及将图像转换，使其与正方体工作。
首先，我所使用的图像大小调整脚本转换为640×640，这似乎是为正方体更易于管理。
-(UIImage *)resizeImage:(UIImage *)image {
CGImageRef imageRef = [image CGImage];
CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(imageRef);
CGColorSpaceRef colorSpaceInfo = CGColorSpaceCreateDeviceRGB();
if (alphaInfo == kCGImageAlphaNone)
alphaInfo = kCGImageAlphaNoneSkipLast;
int width, height;
width = 640;//[image size].width;
height = 640;//[image size].height;
CGContextRef bitmap;
if (image.imageOrientation == UIImageOrientationUp | image.imageOrientation == UIImageOrientationDown) {
bitmap = CGBitmapContextCreate(NULL, width, height, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, alphaInfo);
} else {
bitmap = CGBitmapContextCreate(NULL, height, width, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, alphaInfo);
}
if (image.imageOrientation == UIImageOrientationLeft) {
NSLog(@"image orientation left");
CGContextRotateCTM (bitmap, radians(90));
CGContextTranslateCTM (bitmap, 0, -height);
} else if (image.imageOrientation == UIImageOrientationRight) {
NSLog(@"image orientation right");
CGContextRotateCTM (bitmap, radians(-90));
CGContextTranslateCTM (bitmap, -width, 0);
} else if (image.imageOrientation == UIImageOrientationUp) {
NSLog(@"image orientation up");
} else if (image.imageOrientation == UIImageOrientationDown) {
NSLog(@"image orientation down");
CGContextTranslateCTM (bitmap, width,height);
CGContextRotateCTM (bitmap, radians(-180.));
}
CGContextDrawImage(bitmap, CGRectMake(0, 0, width, height), imageRef);
CGImageRef ref = CGBitmapContextCreateImage(bitmap);
UIImage *result = [UIImage imageWithCGImage:ref];
CGContextRelease(bitmap);
CGImageRelease(ref);
return result;
}
这样的弧度工作，确保您声明它上面的@implementation
static inline double radians (double degrees) {return degrees * M_PI/180;}
然后我转换为灰度。
我发现这篇文章转换图像灰度上转换为灰度。
我从这里成功使用的代码和现在可以读取不同的彩色文本和不同的背景颜色
我已经修改了代码稍微作为一个类中的一个函数，而不是作为自己的类其他人没有工作
- (UIImage *) toGrayscale:(UIImage*)img
{
const int RED = 1;
const int GREEN = 2;
const int BLUE = 3;
// Create image rectangle with current image width/height
CGRect imageRect = CGRectMake(0, 0, img.size.width * img.scale, img.size.height * img.scale);
int width = imageRect.size.width;
int height = imageRect.size.height;
// the pixels will be painted to this array
uint32_t *pixels = (uint32_t *) malloc(width * height * sizeof(uint32_t));
// clear the pixels so any transparency is preserved
memset(pixels, 0, width * height * sizeof(uint32_t));
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
// create a context with RGBA pixels
CGContextRef context = CGBitmapContextCreate(pixels, width, height, 8, width * sizeof(uint32_t), colorSpace,
kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedLast);
// paint the bitmap to our context which will fill in the pixels array
CGContextDrawImage(context, CGRectMake(0, 0, width, height), [img CGImage]);
for(int y = 0; y < height; y++) {
for(int x = 0; x < width; x++) {
uint8_t *rgbaPixel = (uint8_t *) &pixels[y * width + x];
// convert to grayscale using recommended method: http://en.wikipedia.org/wiki/Grayscale#Converting_color_to_grayscale
uint32_t gray = 0.3 * rgbaPixel[RED] + 0.59 * rgbaPixel[GREEN] + 0.11 * rgbaPixel[BLUE];
// set the pixels to gray
rgbaPixel[RED] = gray;
rgbaPixel[GREEN] = gray;
rgbaPixel[BLUE] = gray;
}
}
// create a new CGImageRef from our context with the modified pixels
CGImageRef image = CGBitmapContextCreateImage(context);
// we're done with the context, color space, and pixels
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
free(pixels);
// make a new UIImage to return
UIImage *resultUIImage = [UIImage imageWithCGImage:image
scale:img.scale
orientation:UIImageOrientationUp];
// we're done with image now too
CGImageRelease(image);
return resultUIImage;
}
文章来源: iOS Tesseract OCR Image Preperation
