I'm making a terrain tool.
I made a 2D texture and am using it as a height map.
I want to change a specific part of the heightmap, but I'm having a problem.
I changed certain small parts, but the whole landscape of the texture is changed.
I would like to know the cause of this problem and how to solve it
thank you.
`HeightMap ShaderResourceView Create Code
void TerrainRenderer::BuildHeightmapSRV(ID3D11Device* device)
{
ReleaseCOM(mHeightMapSRV);
ReleaseCOM(m_hmapTex);
D3D11_TEXTURE2D_DESC texDesc;
texDesc.Width = m_terrainData.HeightmapWidth; //basic value 2049
texDesc.Height = m_terrainData.HeightmapHeight; //basic value 2049
texDesc.MipLevels = 1;
texDesc.ArraySize = 1;
texDesc.Format = DXGI_FORMAT_R16_FLOAT;
texDesc.SampleDesc.Count = 1;
texDesc.SampleDesc.Quality = 0;
texDesc.Usage = D3D11_USAGE_DYNAMIC;
texDesc.BindFlags = D3D11_BIND_SHADER_RESOURCE;
texDesc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
texDesc.MiscFlags = 0;
// HALF is defined in xnamath.h, for storing 16-bit float.
std::vector<HALF> hmap(mHeightmap.size());
//current mHeightmap is all zero.
std::transform(mHeightmap.begin(), mHeightmap.end(), hmap.begin(), XMConvertFloatToHalf);
D3D11_SUBRESOURCE_DATA data;
data.pSysMem = &hmap[0];
data.SysMemPitch = m_terrainData.HeightmapWidth * sizeof(HALF);
data.SysMemSlicePitch = 0;
HR(device->CreateTexture2D(&texDesc, &data, &m_hmapTex));
D3D11_SHADER_RESOURCE_VIEW_DESC srvDesc;
srvDesc.Format = texDesc.Format;
srvDesc.ViewDimension = D3D11_SRV_DIMENSION_TEXTURE2D;
srvDesc.Texture2D.MostDetailedMip = 0;
srvDesc.Texture2D.MipLevels = -1;
HR(device->CreateShaderResourceView(m_hmapTex, &srvDesc, &mHeightMapSRV));
}
`HeightMap Texture modifying code
D3D11_MAPPED_SUBRESOURCE mappedData;
//m_hmapTex is ID3D11Texture2D*
HR(m_texMgr.m_context->Map(m_hmapTex, D3D11CalcSubresource(0, 0, 1), D3D11_MAP_WRITE_DISCARD, 0, &mappedData));
HALF* heightMapData = reinterpret_cast<HALF*>(mappedData.pData);
D3D11_TEXTURE2D_DESC heightmapDesc;
m_hmapTex->GetDesc(&heightmapDesc);
UINT width = heightmapDesc.Width;
for (int row = 0; row < width/4; ++row)
{
for (int col = 0; col < width/4; ++col)
{
idx = (row * width) + col;
heightMapData[idx] = static_cast<HALF>(XMConvertFloatToHalf(200));
}
}
m_texMgr.m_context->Unmap(m_hmapTex, D3D11CalcSubresource(0,0,1));
Please refer to the picture below
The lower right area renders the HeightMap texture.
I wanted to edit only 1/4 width and height, but that's all changed.
enter image description here
When the completed heightmap is applied, it works normally.
enter image description here
A texture does not always have the same width and height in memory as the definition suggests. Some textures strides (lines) are oversized. You have to use the Stride Size * Row to calculate the offset to write into.
I have an API that returns the 16-bit Infrared data from a file.
The usage is like this:
UInt16 *irDataResult = IrbGetIrData16([self.path UTF8String]);
The length of the the data pointed by the pointer is : 1024x768x2.
I want to convert it in to an int 2 dimensional array so that I have individual pixels and then I can use one of the UIImage functions to create image out of my raw data.
The I way I'm doing is this:
int dataArray[width][height];
int *dataPointer = &dataArray[0][0];
int byteNum = 0;
for (int w = 0; w < width; w++) {
for (int h = 0; h < height; h++) {
dataArray[w][h] = irDataSource[byteNum] <<0 | irDataSource[byteNum] << 8; //Little endian
byteNum++;
}
}
The loop runs fine, but after a little while it gives my BAD_ACCESS error.
What am I doing wrong?
Also, is this the right approach?
I am checking if UIImage is darker or more whiter . I would like to use this method ,but only to check the third bottom part of the image ,not all of it .
I wonder how exactly to change it to check that,i am not that familiar with the pixels stuff .
BOOL isDarkImage(UIImage* inputImage){
BOOL isDark = FALSE;
CFDataRef imageData = CGDataProviderCopyData(CGImageGetDataProvider(inputImage.CGImage));
const UInt8 *pixels = CFDataGetBytePtr(imageData);
int darkPixels = 0;
long length = CFDataGetLength(imageData);
int const darkPixelThreshold = (inputImage.size.width*inputImage.size.height)*.25;
//should i change here the length ?
for(int i=0; i<length; i+=4)
{
int r = pixels[i];
int g = pixels[i+1];
int b = pixels[i+2];
//luminance calculation gives more weight to r and b for human eyes
float luminance = (0.299*r + 0.587*g + 0.114*b);
if (luminance<150) darkPixels ++;
}
if (darkPixels >= darkPixelThreshold)
isDark = YES;
I can just crop that part of the image, but this will be not efficient way, and wast time .
The solution marked correct here is a more thoughtful approach for getting the pixel data (more tolerant of differing formats) and also demonstrates how to address pixels. With a small adjustment, you can get the bottom of the image as follows:
+ (NSArray*)getRGBAsFromImage:(UIImage*)image
atX:(int)xx
andY:(int)yy
toX:(int)toX
toY:(int)toY {
// ...
int byteIndex = (bytesPerRow * yy) + xx * bytesPerPixel;
int byteIndexEnd = (bytesPerRow * toY) + toX * bytesPerPixel;
while (byteIndex < byteIndexEnd) {
// contents of the loop remain the same
// ...
}
To get the bottom third of the image, call this with xx=0, yy=2.0*image.height/3.0 and toX and toY equal to the image width and height, respectively. Loop the colors in the returned array and compute luminance as your post suggests.
It seems like this should be simpler than I'm finding it to be.
I have an AVFoundation frame coming back in the standard delegate method:
- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
fromConnection:(AVCaptureConnection *)connection
where I would like to convert the frame to greyscale using the Accelerate.Framework.
There is a family of conversion methods in the framework, including vImageConvert_RGBA8888toPlanar8(), which looks like it might be what I would like to see, however, I can't find any examples of how to use them!
So far, I have the code:
- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
fromConnection:(AVCaptureConnection *)connection
{
#autoreleasepool {
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
/*Lock the image buffer*/
CVPixelBufferLockBaseAddress(imageBuffer,0);
/*Get information about the image*/
uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddress(imageBuffer);
size_t width = CVPixelBufferGetWidth(imageBuffer);
size_t height = CVPixelBufferGetHeight(imageBuffer);
size_t stride = CVPixelBufferGetBytesPerRow(imageBuffer);
// vImage In
Pixel_8 *bitmap = (Pixel_8 *)malloc(width * height * sizeof(Pixel_8));
const vImage_Buffer inImage = { bitmap, height, width, stride };
//How can I take this inImage and convert it to greyscale?????
//vImageConvert_RGBA8888toPlanar8()??? Is the correct starting format here??
}
}
So I have two questions:
(1) In the code above, is RBGA8888 the correct starting format?
(2) How can I actually make the Accelerate.Framework call to convert to greyscale?
There is an easier option here. If you change the camera acquire format to YUV, then you already have a greyscale frame that you can use as you like. When setting up your data output, use something like:
dataOutput.videoSettings = #{ (id)kCVPixelBufferPixelFormatTypeKey : #(kCVPixelFormatType_420YpCbCr8BiPlanarFullRange) };
You can then access the Y plane in your capture callback using:
CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CVPixelBufferLockBaseAddress(pixelBuffer, kCVPixelBufferLock_ReadOnly);
uint8_t *yPlane = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0);
... do stuff with your greyscale camera image ...
CVPixelBufferUnlockBaseAddress(pixelBuffer);
The vImage method is to use vImageMatrixMultiply_Planar8 and a 1x3 matrix.
vImageConvert_RGBA8888toPlanar8 is the function you use to convert a RGBA8888 buffer into 4 planar buffers. These are used by vImageMatrixMultiply_Planar8. vImageMatrixMultiply_ARGB8888 will do it too in one pass, but your gray channel will be interleaved with three other channels in the result. vImageConvert_RGBA8888toPlanar8 itself doesn't do any math. All it does is separate your interleaved image into separate image planes.
If you need to adjust the gamma as well, then probably vImageConvert_AnyToAny() is the easy choice. It will do the fully color managed conversion from your RGB format to a grayscale colorspace. See vImage_Utilities.h.
I like Tarks answer better though. It just leaves you in a position of having to color manage the Luminance manually (if you care).
Convert BGRA Image to Grayscale with Accelerate vImage
This method is meant to illustrate getting Accelerate's vImage use in converting BGR images to grayscale. Your image may very well be in RGBA format and you'll need to adjust the matrix accordingly, but the camera outputs BGRA so I'm using it here. The values in the matrix are the same values used in OpenCV for cvtColor, there are other values you might play with like luminosity. I assume you malloc the appropriate amount of memory for the result. In the case of grayscale it is only 1-channel or 1/4 the memory used for BGRA. If anyone finds issues with this code please leave a comment.
Performance note
Converting to grayscale in this way may NOT be the fastest. You should check the performance of any method in your environment. Brad Larson's GPUImage might be faster, or even OpenCV's cvtColor. In any case you will want to remove the calls to malloc and free for the intermediate buffers and manage them for the app lifecycle. Otherwise, the function call will be dominated by the malloc and free. Apple's docs recommend reusing the whole vImage_Buffer when possible.
You can also read about solving the same problem with NEON intrinsics.
Finally, the fastest method is not converting at all. If you're getting image data from the device camera the device camera is natively in the kCVPixelFormatType_420YpCbCr8BiPlanarFullRange format. Meaning, grabbing the first plane's data (Y-Channel, luma) is the fastest way to get grayscale.
BGRA to Grayscale
- (void)convertBGRAFrame:(const CLPBasicVideoFrame &)bgraFrame toGrayscale:(CLPBasicVideoFrame &)grayscaleFrame
{
vImage_Buffer bgraImageBuffer = {
.width = bgraFrame.width,
.height = bgraFrame.height,
.rowBytes = bgraFrame.bytesPerRow,
.data = bgraFrame.rawPixelData
};
void *intermediateBuffer = malloc(bgraFrame.totalBytes);
vImage_Buffer intermediateImageBuffer = {
.width = bgraFrame.width,
.height = bgraFrame.height,
.rowBytes = bgraFrame.bytesPerRow,
.data = intermediateBuffer
};
int32_t divisor = 256;
// int16_t a = (int16_t)roundf(1.0f * divisor);
int16_t r = (int16_t)roundf(0.299f * divisor);
int16_t g = (int16_t)roundf(0.587f * divisor);
int16_t b = (int16_t)roundf(0.114f * divisor);
const int16_t bgrToGray[4 * 4] = { b, 0, 0, 0,
g, 0, 0, 0,
r, 0, 0, 0,
0, 0, 0, 0 };
vImage_Error error;
error = vImageMatrixMultiply_ARGB8888(&bgraImageBuffer, &intermediateImageBuffer, bgrToGray, divisor, NULL, NULL, kvImageNoFlags);
if (error != kvImageNoError) {
NSLog(#"%s, vImage error %zd", __PRETTY_FUNCTION__, error);
}
vImage_Buffer grayscaleImageBuffer = {
.width = grayscaleFrame.width,
.height = grayscaleFrame.height,
.rowBytes = grayscaleFrame.bytesPerRow,
.data = grayscaleFrame.rawPixelData
};
void *scratchBuffer = malloc(grayscaleFrame.totalBytes);
vImage_Buffer scratchImageBuffer = {
.width = grayscaleFrame.width,
.height = grayscaleFrame.height,
.rowBytes = grayscaleFrame.bytesPerRow,
.data = scratchBuffer
};
error = vImageConvert_ARGB8888toPlanar8(&intermediateImageBuffer, &grayscaleImageBuffer, &scratchImageBuffer, &scratchImageBuffer, &scratchImageBuffer, kvImageNoFlags);
if (error != kvImageNoError) {
NSLog(#"%s, vImage error %zd", __PRETTY_FUNCTION__, error);
}
free(intermediateBuffer);
free(scratchBuffer);
}
CLPBasicVideoFrame.h - For reference
typedef struct
{
size_t width;
size_t height;
size_t bytesPerRow;
size_t totalBytes;
unsigned long pixelFormat;
void *rawPixelData;
} CLPBasicVideoFrame;
I got through the grayscale conversion, but was having trouble with the quality when I found this book on the web called Instant OpenCV for iOS. I personally picked up a copy and it has a number of gems, although the code is bit of a mess. On the bright-side it is a very reasonably priced eBook.
I'm very curious about that matrix. I toyed around with it for hours trying to figure out what the arrangement should be. I would have thought the values should be on the diagonal, but the Instant OpenCV guys put it as above.
if you need to use BGRA vide streams - you can use this excellent conversion
here
This is the function you'll need to take:
void neon_convert (uint8_t * __restrict dest, uint8_t * __restrict src, int numPixels)
{
int i;
uint8x8_t rfac = vdup_n_u8 (77);
uint8x8_t gfac = vdup_n_u8 (151);
uint8x8_t bfac = vdup_n_u8 (28);
int n = numPixels / 8;
// Convert per eight pixels
for (i=0; i < n; ++i)
{
uint16x8_t temp;
uint8x8x4_t rgb = vld4_u8 (src);
uint8x8_t result;
temp = vmull_u8 (rgb.val[0], bfac);
temp = vmlal_u8 (temp,rgb.val[1], gfac);
temp = vmlal_u8 (temp,rgb.val[2], rfac);
result = vshrn_n_u16 (temp, 8);
vst1_u8 (dest, result);
src += 8*4;
dest += 8;
}
}
more optimisations (using assembly) are in the link
(1) My experience with the iOS camera framework has been with images in the kCMPixelFormat_32BGRA format, which is compatible with the ARGB8888 family of functions. (It may be possible to use other formats as well.)
(2) The simplest way to convert from BGR to grayscale on iOS is to use vImageMatrixMultiply_ARGB8888ToPlanar8():
https://developer.apple.com/documentation/accelerate/1546979-vimagematrixmultiply_argb8888top
Here is a fairly complete example written in Swift. I'm assuming the Objective-C code would be similar.
guard let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else {
// TODO: report error
return
}
// Lock the image buffer
if (kCVReturnSuccess != CVPixelBufferLockBaseAddress(imageBuffer, CVPixelBufferLockFlags.readOnly)) {
// TODO: report error
return
}
defer {
CVPixelBufferUnlockBaseAddress(imageBuffer, CVPixelBufferLockFlags.readOnly)
}
// Create input vImage_Buffer
let baseAddress = CVPixelBufferGetBaseAddress(imageBuffer)
let width = CVPixelBufferGetWidth(imageBuffer)
let height = CVPixelBufferGetHeight(imageBuffer)
let stride = CVPixelBufferGetBytesPerRow(imageBuffer)
var inImage = vImage_Buffer(data: baseAddress, height: UInt(height), width: UInt(width), rowBytes: stride)
// Create output vImage_Buffer
let bitmap = malloc(width * height)
var outImage = vImage_Buffer(data: bitmap, height: UInt(height), width: UInt(width), rowBytes: width)
defer {
// Make sure to free unless the caller is responsible for this
free(bitmap)
}
// Arbitrary divisor to scale coefficients to integer values
let divisor: Int32 = 0x1000
let fDivisor = Float(divisor)
// Rec.709 coefficients
var coefficientsMatrix = [
Int16(0.0722 * fDivisor), // blue
Int16(0.7152 * fDivisor), // green
Int16(0.2126 * fDivisor), // red
0 // alpha
]
// Convert to greyscale
if (kvImageNoError != vImageMatrixMultiply_ARGB8888ToPlanar8(
&inImage, &outImage, &coefficientsMatrix, divisor, nil, 0, vImage_Flags(kvImageNoFlags))) {
// TODO: report error
return
}
The code above was inspired by a tutorial from Apple on grayscale conversion, which can be found at the following link. It also includes conversion to a CGImage if that is needed. Note that they assume RGB order instead of BGR, and they only provide a 3 coefficients instead of 4 (mistake?)
https://developer.apple.com/documentation/accelerate/vimage/converting_color_images_to_grayscale
I'm working on a drawing app for iPad using Cocos-iOS and I'm having performance issues with drawing lines as a type of CCNode. I understand that using draw in a node causes it to be called every time the canvas is repainted and the current code is very heavy if used every time:
for (LineNodePoint *point in self.points) {
start = end;
end = point;
if (start && end) {
float distance = ccpDistance(start.point, end.point);
if (distance > 1) {
int d = (int)distance;
float difx = end.point.x - start.point.x;
float dify = end.point.y - start.point.y;
for (int i = 0; i < d; i++) {
float delta = i / distance;
[[self.brush sprite] setPosition:ccp(start.point.x + (difx * delta), start.point.y + (dify * delta))];
[[self.brush sprite] visit];
}
}
}
}
Very heavy...
I either need a better way to draw the lines or to be able to cache the drawing as a raster.
Thanks in advance for any help.
How about ccDrawLine or CCMutableTexture? CCMutableTexture is for manipulating pixels using CCRenderTexture internally as you said.
ccDrawLine
cocos2d for iPhone 1.0.0 API reference
CCMutableTexture
Fast set/getPixel for an opengl texture?
[render texture] pixel manipulation (integrated CCMutableTexture functionality)