screenShot代码不适用于ipad,适用于iphone
Posted
技术标签:
【中文标题】screenShot代码不适用于ipad,适用于iphone【英文标题】:screenShot code Not working on ipad, works on iphone 【发布时间】:2011-07-14 11:29:24 【问题描述】:我遇到了这个奇怪的问题... 我必须捕获屏幕数据并使用以下代码将其转换为图像..此代码在 iphone/ipad 模拟器和 iphone 设备上运行良好,但不适用于 iPad。 iphone 设备是 ios 版本 3.1.1 而 ipad 是 ios 4.2...
- (UIImage *)screenshotImage
CGRect screenBounds = [[UIScreen mainScreen] bounds];
int backingWidth = screenBounds.size.width;
int backingHeight =screenBounds.size.height;
NSInteger myDataLength = backingWidth * backingHeight * 4;
GLuint *buffer = (GLuint *) malloc(myDataLength);
glReadPixels(0, 0, backingWidth, backingHeight, GL_RGBA4, GL_UNSIGNED_BYTE, buffer);
for(int y = 0; y < backingHeight / 2; y++)
for(int xt = 0; xt < backingWidth; xt++)
GLuint top = buffer[y * backingWidth + xt];
GLuint bottom = buffer[(backingHeight - 1 - y) * backingWidth + xt];
buffer[(backingHeight - 1 - y) * backingWidth + xt] = top;
buffer[y * backingWidth + xt] = bottom;
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer, myDataLength, releaseScreenshotData);
const int bitsPerComponent = 8;
const int bitsPerPixel = 4 * bitsPerComponent;
const int bytesPerRow = 4 * backingWidth;
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
CGImageRef imageRef = CGImageCreate(backingWidth,backingHeight, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
CGColorSpaceRelease(colorSpaceRef);
CGDataProviderRelease(provider);
UIImage *myImage = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
// myImage = [self addIconToImage:myImage];
return myImage;
知道出了什么问题吗..??
【问题讨论】:
【参考方案1】:这两行不匹配
NSInteger myDataLength = backingWidth * backingHeight * 4;
glReadPixels(0, 0, backingWidth, backingHeight, GL_RGBA4, GL_UNSIGNED_BYTE, buffer);
GL_RGB4
表示每个通道 4 位,但是您为每个通道分配 8 位。正确的令牌是GL_RGB8
。在 iPhone 上,GL_RGB4
可能不受支持并回退到 GL_RGBA
。
还要确保您正在从正确的缓冲区读取数据(正面与左侧与任何(意外)绑定的 FBO)。我建议在进行缓冲区交换之前从后台缓冲区读取数据。
【讨论】:
k 感谢您的快速回复.. 现在我已将 GL_RGB4 更改为 GL_RGBA。代码在 iphone 设备上运行良好,但在 ipad 设备上运行良好不知道是什么问题....我在两个设备上使用相同的代码 将其更改为 GL_RGBA8,而不仅仅是 GL_RGBA(注意“8”)。 嘿,我的 xcode 并没有准确地给我 GL_RGBA8 的选项,而是给了 GL_RGBA8_OES 作为选项..当我使用这个 GL_RGBA8_OES 时,它给出了编译时错误“”GL_RGBA8_OES 没有在这个范围内定义“” @Tornado:包含 OES 标头? Hmmmm .. Opengl 框架包含在项目中...我已经包含了#import对于 ios 4 或更高版本,我使用多采样技术进行抗锯齿 ....glReadpixels() 无法直接从 multiSampled FBO 读取,您需要将其解析为单采样缓冲区,然后尝试读取它...请参考到以下帖子:-
Reading data using glReadPixel() with multisampling
【讨论】:
【参考方案3】:openGL ES 苹果文档截图
- (UIImage*)snapshot:(UIView*)eaglview
GLint backingWidth, backingHeight;
// Bind the color renderbuffer used to render the OpenGL ES view
// If your application only creates a single color renderbuffer which is already bound at this point,
// this call is redundant, but it is needed if you're dealing with multiple renderbuffers.
// Note, replace "_colorRenderbuffer" with the actual name of the renderbuffer object defined in your class.
glBindRenderbufferOES(GL_RENDERBUFFER_OES, _colorRenderbuffer);
// Get the size of the backing CAEAGLLayer
glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_WIDTH_OES, &backingWidth);
glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backingHeight);
NSInteger x = 0, y = 0, width = backingWidth, height = backingHeight;
NSInteger dataLength = width * height * 4;
GLubyte *data = (GLubyte*)malloc(dataLength * sizeof(GLubyte));
// Read pixel data from the framebuffer
glPixelStorei(GL_PACK_ALIGNMENT, 4);
glReadPixels(x, y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, data);
// Create a CGImage with the pixel data
// If your OpenGL ES content is opaque, use kCGImageAlphaNoneSkipLast to ignore the alpha channel
// otherwise, use kCGImageAlphaPremultipliedLast
CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, data, dataLength, NULL);
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
CGImageRef iref = CGImageCreate(width, height, 8, 32, width * 4, colorspace, kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast,
ref, NULL, true, kCGRenderingIntentDefault);
// OpenGL ES measures data in PIXELS
// Create a graphics context with the target size measured in POINTS
NSInteger widthInPoints, heightInPoints;
if (NULL != UIGraphicsBeginImageContextWithOptions)
// On iOS 4 and later, use UIGraphicsBeginImageContextWithOptions to take the scale into consideration
// Set the scale parameter to your OpenGL ES view's contentScaleFactor
// so that you get a high-resolution snapshot when its value is greater than 1.0
CGFloat scale = eaglview.contentScaleFactor;
widthInPoints = width / scale;
heightInPoints = height / scale;
UIGraphicsBeginImageContextWithOptions(CGSizeMake(widthInPoints, heightInPoints), NO, scale);
else
// On iOS prior to 4, fall back to use UIGraphicsBeginImageContext
widthInPoints = width;
heightInPoints = height;
UIGraphicsBeginImageContext(CGSizeMake(widthInPoints, heightInPoints));
CGContextRef cgcontext = UIGraphicsGetCurrentContext();
// UIKit coordinate system is upside down to GL/Quartz coordinate system
// Flip the CGImage by rendering it to the flipped bitmap context
// The size of the destination area is measured in POINTS
CGContextSetBlendMode(cgcontext, kCGBlendModeCopy);
CGContextDrawImage(cgcontext, CGRectMake(0.0, 0.0, widthInPoints, heightInPoints), iref);
// Retrieve the UIImage from the current context
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// Clean up
free(data);
CFRelease(ref);
CFRelease(colorspace);
CGImageRelease(iref);
return image;
【讨论】:
以上是关于screenShot代码不适用于ipad,适用于iphone的主要内容,如果未能解决你的问题,请参考以下文章
我逐字复制了 UIPopoverController 代码,该代码适用于 xcode 3.2 上的 ipad,但不适用于 xcode 4.2
JayData / Phonegap 适用于 iPad 模拟器但不适用于 iPad 设备
Swift pushViewController 适用于 iPad 但不适用于 iPhone