Add a thumbnail sample (#17)

.gitignore

@@ -11,3 +11,6 @@ logo*
 native_libs/lib*
 includes.txt
 includes_filtered.txt
+hs_err*
+
+sample_run

sample/src/main/kotlin/vipsffm/CreateThumbnailSample.kt

@@ -0,0 +1,114 @@
+package vipsffm
+
+import app.photofox.vipsffm.generated.VipsImage
+import app.photofox.vipsffm.generated.vips_h.vips_init
+import app.photofox.vipsffm.generated.vips_h.vips_thumbnail
+import app.photofox.vipsffm.generated.vips_h_1.C_POINTER
+import app.photofox.vipsffm.generated.vips_h_1.vips_error_buffer
+import app.photofox.vipsffm.generated.vips_h_1.vips_image_new_from_file
+import app.photofox.vipsffm.generated.vips_h_1.vips_image_write_to_file
+import vipsffm.GetVersionSample.logger
+import java.lang.foreign.Arena
+import java.lang.foreign.MemorySegment
+import java.lang.foreign.ValueLayout
+import java.nio.file.Files
+import java.nio.file.Path
+import java.nio.file.Paths
+import kotlin.io.path.absolutePathString
+
+object CreateThumbnailSample: RunnableSample {
+
+    override fun run(arena: Arena, workingDirectory: Path): Result<Unit> {
+        val result = vips_init(arena.allocateFrom("vips-ffm"))
+        if (result != 0) {
+            return Result.failure(
+                RuntimeException("failed to initialise libvips, code $result")
+            )
+        }
+
+        val sourcePath = Paths.get("sample/src/main/resources/sample_images/rabbit.jpg")
+        val sourcePathC = arena.allocateFrom(sourcePath.absolutePathString())
+        if (!Files.exists(sourcePath)) {
+            return Result.failure(
+                RuntimeException("source image doesn't exist")
+            )
+        }
+
+        val newImageFromFileInvoker = vips_image_new_from_file.makeInvoker(C_POINTER)
+        val sourceImage = newImageFromFileInvoker.apply(arena.allocateFrom(sourcePath.absolutePathString()),
+            MemorySegment.NULL)
+        if (sourceImage == MemorySegment.NULL) {
+            val error = vips_error_buffer().getString(0)
+            logger.error("failed to load image at $sourcePath, error: {}", error)
+            return Result.failure(
+                RuntimeException("failed to load image")
+            )
+        }
+        val sourceWidth = VipsImage.Xsize(sourceImage)
+        val sourceHeight = VipsImage.Ysize(sourceImage)
+        logger.info("source image size: $sourceWidth x $sourceHeight")
+
+        val writeSameInvoker = vips_image_write_to_file.makeInvoker(C_POINTER)
+        val samePath = workingDirectory.resolve("rabbit_copy.jpg")
+        val sameResult = writeSameInvoker.apply(sourceImage, arena.allocateFrom(samePath.absolutePathString()),
+            MemorySegment.NULL)
+        if (sameResult != 0) {
+            val error = vips_error_buffer().getString(0)
+            logger.error("failed to copy image, error: {}", error)
+            return Result.failure(
+                RuntimeException("failed to copy image, code $sameResult")
+            )
+        }
+
+        // VipsImage**
+        val outputImagePointer = arena.allocate(ValueLayout.ADDRESS)
+
+        val thumbnailInvoker = vips_thumbnail.makeInvoker(C_POINTER)
+        val makeThumbnailResult = thumbnailInvoker.apply(sourcePathC, outputImagePointer, 400, MemorySegment.NULL)
+        if (makeThumbnailResult != 0) {
+            val error = vips_error_buffer().getString(0)
+            logger.error("failed to make thumbnail, error: {}", error)
+            return Result.failure(
+                RuntimeException("failed to make thumbnail, code $makeThumbnailResult")
+            )
+        }
+
+        val resultingOutputImagePointer = outputImagePointer.get(C_POINTER, 0)
+        val resultingOutputImage = VipsImage.reinterpret(resultingOutputImagePointer, arena, null)
+
+        val outputWidth = VipsImage.Xsize(resultingOutputImage)
+        val outputHeight = VipsImage.Ysize(resultingOutputImage)
+        logger.info("output image size: $outputWidth x $outputHeight")
+
+        val thumbnailPath = workingDirectory.resolve("rabbit_thumbnail_400.jpg")
+        val thumbnailPathC = arena.allocateFrom(thumbnailPath.absolutePathString())
+        val writeToFileInvoker = vips_image_write_to_file.makeInvoker(C_POINTER)
+        val writeToFileResult = writeToFileInvoker.apply(resultingOutputImage, thumbnailPathC, MemorySegment.NULL)
+        if (writeToFileResult != 0) {
+            val error = vips_error_buffer().getString(0)
+            logger.error("failed to write thumbnail, error: {}", error)
+            return Result.failure(
+                RuntimeException("failed to write thumbnail, code $writeToFileResult")
+            )
+        }
+
+        return validate(thumbnailPath)
+    }
+
+    private fun validate(thumbnailPath: Path): Result<Unit> {
+        if (!Files.exists(thumbnailPath)) {
+            return Result.failure(
+                RuntimeException("wrote thumbnail, but failed to find at \"$thumbnailPath\"")
+            )
+        }
+
+        val fileSizeKb = Files.size(thumbnailPath) / 1000
+        if (fileSizeKb < 20 || fileSizeKb > 100) {
+            return Result.failure(
+                RuntimeException("unexpected resulting thumbnail size $fileSizeKb")
+            )
+        }
+
+        return Result.success(Unit)
+    }
+}

sample/src/main/kotlin/vipsffm/VipsFfm.kt

@@ -14,7 +14,8 @@ object VipsFfm {
     @JvmStatic
     fun main(args: Array<String>) {
         val samples = listOf(
-            GetVersionSample
+            GetVersionSample,
+            CreateThumbnailSample
         )
         val sampleParentRunPath = Paths.get("sample_run")
         if (Files.exists(sampleParentRunPath)) {

sample/src/main/resources/sample_images/fox_license.txt

@@ -0,0 +1,3 @@
+Author: Jonathen Pie https://unsplash.com/@r3dmax - https://unsplash.com/photos/NBvcQRdRSeQ
+Original source: https://en.wikipedia.org/wiki/Arctic_fox#/media/File:Iceland-1979445_(cropped_3).jpg
+License: http://creativecommons.org/publicdomain/zero/1.0/deed.en

sample/src/main/resources/sample_images/rabbit_license.txt

@@ -0,0 +1,3 @@
+Author: https://commons.wikimedia.org/wiki/User:Alur%C3%ADn
+Original source: https://en.wikipedia.org/wiki/Rabbit#/media/File:Oryctolagus_cuniculus_Rcdo.jpg
+License: https://creativecommons.org/licenses/by/3.0/