從XCode中的Objective C中使用libjpeg

基本上我正在做一個最佳圖像大小的屏幕截圖應用程序。從XCode中的Objective C中使用libjpeg

我想要捕獲我的Mac屏幕並將其保存爲JPEG文件。我想用Cocoa API捕捉屏幕[CGWindowListCreateImage]並使用libjpeg9將文件保存爲JPEG格式。我使用XCode中的「Add Files to Project_Name」選項包含靜態庫[libjpeg.a]和頭文件[jpeglib.h，jconfig.h，jerror.h和jmorecfg.h]。

我用來保存爲JPEG文件的代碼是

int write_jpeg_file(char *filename) 
{ 
    struct jpeg_compress_struct cinfo; 
    struct jpeg_error_mgr jerr; 

    /* this is a pointer to one row of image data */ 
    JSAMPROW row_pointer[1]; 
    FILE *outfile = fopen(filename, "wb"); 

    if (!outfile) 
    { 
     printf("Error opening output jpeg file %s\n!", filename); 
     return -1; 
    } 
    cinfo.err = jpeg_std_error(&jerr); 
    jpeg_create_compress(&cinfo); 
    jpeg_stdio_dest(&cinfo, outfile); 

    /* Setting the parameters of the output file here */ 
    cinfo.image_width = width; 
    cinfo.image_height = height; 
    cinfo.input_components = bytes_per_pixel; 
    cinfo.in_color_space = color_space; 
    /* default compression parameters, we shouldn't be worried about these */ 
    jpeg_set_defaults(&cinfo); 
    /* Now do the compression .. */ 
    jpeg_start_compress(&cinfo, TRUE); 
    /* like reading a file, this time write one row at a time */ 
    while(cinfo.next_scanline < cinfo.image_height) 
    { 
     row_pointer[0] = &raw_image[ cinfo.next_scanline * cinfo.image_width * cinfo.input_components]; 
     jpeg_write_scanlines(&cinfo, row_pointer, 1); 
    } 
    /* similar to read file, clean up after we're done compressing */ 
    jpeg_finish_compress(&cinfo); 
    jpeg_destroy_compress(&cinfo); 
    fclose(outfile); 
    /* success code is 1! */ 
    return 1; 
}

當我生成和運行項目我收到以下錯誤

解析問題

預計}

在線

typedef enum {FALSE = 0，TRUE = 1} boolean;

在jmorecfg.h這是libjpeg頭文件。我不知道爲什麼我得到這個錯誤。請幫幫我。

我知道有一種方法可以使用Cocoa API來保存文件，而不是使用libjpeg。我第一次嘗試使用Cocoa的XCode。我能夠獲得JPEG文件。文件大小相對較大（〜200KB）。當我使用libjpeg在C中創建圖像時，文件大小爲〜100KB。

的代碼我使用：

CGFloat imageCompression = 0.6; 

- (NSImage *)captureImageForRect:(NSRect)rect { 
    CGImageRef screenShot = CGWindowListCreateImage(CGRectInfinite, kCGWindowListOptionOnScreenOnly, kCGNullWindowID, kCGWindowImageDefault); 
    NSBitmapImageRep *imageRep = [[NSBitmapImageRep alloc] initWithCGImage:screenShot]; 
    NSLog(@"Bits per pixel : %ld", [imageRep bitsPerPixel]); 
    NSImage *result = [[NSImage alloc] init]; 
    [result addRepresentation:imageRep]; 
    screenShot=nil; 
    imageRep=nil; 
    return result; 
} 

-(NSData *)jpegReresentationOfImage:(NSImage *) image { 
    NSBitmapImageRep* myBitmapImageRep=nil; 
    NSSize imageSize = [image size]; 
    [image lockFocus]; 
    NSRect imageRect = NSMakeRect(0, 0, imageSize.width, imageSize.height); 
    myBitmapImageRep = [[NSBitmapImageRep alloc] initWithFocusedViewRect:imageRect]; 
    [image unlockFocus]; 

    // set up the options for creating a JPEG 
    NSDictionary* options = [NSDictionary dictionaryWithObjectsAndKeys: 
        [NSNumber numberWithDouble:imageCompression], NSImageCompressionFactor, 
        [NSNumber numberWithBool:NO], NSImageProgressive, 
        nil]; 

    NSData* imageData = [myBitmapImageRep representationUsingType:NSJPEGFileType properties:options]; 
    myBitmapImageRep=nil; 
    return (imageData); 
} 


-(void)captureAndSave { 
    NSString *fileName = @"/Volumes/Official/images/output/Mac_Window_1.jpg"; 
    NSImage *screenshot = [self captureImageForRect:[[NSScreen mainScreen] frame]]; 
    NSData *jpgRep = [self jpegReresentationOfImage:screenshot]; 
    [jpgRep writeToFile:[fileName stringByExpandingTildeInPath] atomically:NO]; 
    [NSApp terminate:self]; 
}

來源

2013-08-01 Senthil Ganesh

總之，如何在XCode中使用libjpeg？ –

添加以下行jconfig.h解決了這個問題。添加後，我沒有收到編譯錯誤，我可以在我的Objetive-C程序中使用libjpeg。

的#define USE_MAC_MEMMGR

在jmemmac.c，我發現下面的代碼，幫我解決這個問題。只需添加上面的行就行了！

#ifndef USE_MAC_MEMMGR /* make sure user got configuration right */ 
    You forgot to define USE_MAC_MEMMGR in jconfig.h. /* deliberate syntax error */ 
#endif

來源

2014-02-24 10:32:47

從XCode中的Objective C中使用libjpeg

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